Important Questions
1. List out the apparatus required to verify that is constant for a conductor. Explain the experiment with help of a diagram.
(OR)
'At constant temperature, the potential difference between the ends of a conductor is directly proportional to the current passing through it'. To verify this experimentally which apparatus are required? Explain it with the help of a diagram. (AS 3) 4 Marks
A: AIM: To show that the ratio is constant for a conductor.
Material required: 5 dry cells of 1.5 V each, conducting wires, an ammeter, a voltmeter, thin manganin spoke of length 10 cm and key.
Procedure:
‣ Connect a circuit as shown in the figure.
‣ Solder the conducting wires to the ends of the manganin spoke.
‣ Close the key. Note the readings of current (I) from ammeter and potential difference (V) from voltmeter in the table given below.
‣ Now connect two cells in the circuit and note the respective readings of ammeter and voltmeter in the above table.
‣ Repeat the above procedure using three cells and four cells and five cells respectively.
‣ Record the values of potential difference (V) and current (I) corresponding to each case in the above table.
‣ Find for each set of values.
‣ We notice that is a constant.
V I
‣ From this we can conclude that the potential difference between the ends of the manganin spoke is directly proportional to the current passing through it. The temperature of the manganin spoke is constant during the flow.
2. On what factors does the resistance of a conductor depend? How can you verify experimentally that any one of the factor affects the resistance. (AS 3) 4 Marks
A: The resistance of a conductor depends on nature of material and dimensions such as length, area of cross - section and temperature.
Verifying experimentally that resistance of a conductor depends on temperature:
‣ Take a bulb and measure the resistance of the bulb using a multimeter in open circuit. Note the value of resistance.
‣ Now connect the bulb in a circuit and switch on the circuit.
‣ After few minutes the bulb gets heated.
‣ Now measure the resistance of the bulb again with multimeter.
‣ The value of resistance of the bulb in second instance is more than the resistance of the bulb in open circuit.
‣ Here the increase in temperature of the filament in the bulb is responsible for increase in resistance of the bulb.
‣ Thus the value of resistance of a conductor depends on the temperature.
3. How can you verify experimentally that the resistance of a conductor depends upon nature of material. (AS 3) 4 Marks
A: Different metal rods are connected between P and Q
‣ Collect different metal rods of the same length and same cross sectional area like copper, aluminium, iron etc.
‣ Make circuit leaving gap between P and Q as shown in figure.
‣ Connect one of the metal rods between P and Q and switch on the circuit.
‣ Measure the current using an ammeter and note the value.
‣ Repeat this with other metal rods and measure electric current in each case.
‣ The values of current are different for different metal rods for a constant potential difference.
‣ From this we conclude that the resistance of a conductor depends on the material of the conductor.
4. Write the list of apparatus required to verify experimentally that the resistance of a conductor is inversely proportional to cross section Area. Write the procedure of the experiment with the help of a diagram. (AS 3) 4 Marks
A: Required Materials: Battery, Ammeter, Key, Wires, Iron rods with different cross - section areas (lengths must be same).
Procedure:
‣ Collect iron rods of equal lengths but different cross - section areas.
‣ Make a circuit leaving gap between P and Q as shown in figure.
‣ Connect one of the rods between P and Q and measure the current using ammeter and note the values.
‣ Repeat this with the other rods and note the corresponding values of current in each case and note them.
‣ We will notice that the current flowing through the rod increases with increasing in the cross section area of the rod.
‣ Thus the resistance of the rod decreases with increasing the cross - section area.
‣ From this we can conclude that the resistance (R) of a conductor is inversely proportional to its cross-section area (A).
R (at constant temperature and length of the conductor).
5. Show that effective resistance of a series combination in a circuit is equal to sum of their resistances. (AS 1) 4 Marks
A: Series connection: In a circuit, resistors connected end to end are said to be in series, if the same current exists in all of them through a single path.
* Consider three resistors R_{1}, R_{2}, R_{3} are connected in series.
* V1, V2 and V3 are the potential difference across the resistances R_{1}, R_{2} and R_{3} respectively.
* Let I be the current flowing through each of the resistance.
* 'V' is the total potential difference in the circuit.
.^{.}. V = V_{1} + V_{2} + V_{3} .......... (1)
By Ohm's law
V_{1} = IR_{1}, V_{2} = IR_{2}, V_{3 }= IR_{3}
Substitute the values of V_{1}, V_{2} and V_{3} in equation (1)
V = IR_{1} + IR_{2} + IR_{3} .......... (2)
Let R_{eq} is the equivalent resistance of the combination of resistors in series.
So, we have V = IR_{eq}
From equation ..... 2
I R_{eq} = IR_{1} + IR_{2} + IR_{3}
I(R_{eq}) = I(R_{1} + R_{2} + R_{3})
R_{eq} = R_{1} + R_{2} + R_{3}
* The sum of individual resistance is equal to their equivalent resistance when the resistors are connected in series.
6. Show that the reciprocal of the effective resistance of a parallel combination in a circuit is equal to the sum of the reciprocals of individual resistances.
(OR)
Explain the expression for the equivalent resistance of three resistors which are connected in parallel. 4 Marks
A: Parallel connection: In a circuit , resistors connected to common terminals are said to be in parallel, if identical potential difference exists across all of them.
* Consider three resistors R_{1}, R_{2} and R_{3} connected in parallel.
* Suppose a current I flows through the circuit when a cell of voltage 'V' is connected across the combination.
* The current I is divided as I_{1}, I_{2}, and I_{3} which are flow through R_{1}, R_{2} and R_{3} respectively.
I = I_{1} + I_{2} + I_{3} ..... (1)
By Ohm's law
Substituting the values of I_{1}, I_{2} and I_{3} in equation (1)
Let R_{eq} be the equivalent resistance of the resistor is parallel.
^{V Then we get I = }_{}
From equation (2)
* The reciprocal of the equivalent resistance of the combination is equal to the sum of the reciprocals of the individual resistances.
7. State junction law and loop law and explain each law with one suitable example. (AS 1) 4 Marks
A: i) Junction Law: At any junction point in a circuit where the current can divide, the sum of the currents in to the junction must equal. To the sum of the currents leaving the junction. This means that there is no accumulation of electric charges at any junction in a circuit.
I_{1}, I_{4} and I_{6} are the currents into the junction.
I_{2}, I_{3} and I_{5} are the currents leaving the junction according to junction law.
I_{1} + I_{4} + I_{6} = I_{2} + I_{3} + I_{5}
ii) Loop Law: The algebraic sum of the increases and decreases in potential difference across various components of the circuit in a closed circuit loop must be zero.
Let us apply law to the circuit shown in figure.
i) For the loop ABCDEFA:
The resultant potential difference in the loop is
-V_{1} + I_{1}R_{1} - I_{2}R_{2} + V_{2} = 0
ii) For the loop AFEDCBA:
The resultant potential difference in the loop is
-V_{2} + I_{2}R_{2} - I_{1}R_{1} + V_{1} = 0
8. What do you understand about overload? Explain?
(OR)
Why does the electrical appliances damages due to overload? How can we prevent the damages due to overload? (AS 1) (AS 6) 4 Marks
A: Overload of Current:
If the total current drawn from the mains is equal to the sum of the current passing through each device.
If we add more devices to the household circuit the current drawn from the mains also increases. Then over heating occurs and may cause a fire. This is called overloading.
for Example:
* In our houses, the maximum current can be drawn from the mains is 5 - 20 A and potential difference is 240 V.
* When the current drawn from the mains is more than 20 A, caused overloading, devices may damages.
* From the given figure, if we switch on devices, such as heater, the current drawn from the mains exceeds the maximum limit 20 A.
* It causes fire.
* To prevent damages due to overloading, we connect an electric fuse to the household circuit, as shown in figure. In this arrangement, the entire current from the mains must pass through the fuse.
* The fuse consists of a thin wire of low melting point. When the current in the fuse exceeds 20 A, the wire will heat up and melt. The circuit then becomes open and prevents the flow of current into the household circuit. So, all the electric devices are saved from damage that could be caused by overload.
9. Imagine that you have three resistors of R Ω each. How many resultant resistances can be obtained by connecting these three in different ways? Draw the relevant diagrams. (AS 5) 4 Marks
A: We can connect these three resistor in four ways.
i) Connecting them in series.
10. Explain the effects of electric shock on human body? (AS 1) (AS 6) 4 Marks
A: The current passing through our body when we touch alive wire of 240 V is given by I = 0.0024 A. When this quantity of current flows through the body the functioning of organs inside the body gets disturbed. This disturbance inside the body is felt as electric shock.
If the current flows continues further it damages the tissues of the body. which leads to decrease in resistance of the body when this current flows for a longer time damage to the tissues increases and thereby the resistance of human body decreases further. Hence, the current through the human body will increase. If this current reaches 0.07 A, it effects the functioning of the heart and if this much current passes through the heart for more than one second it could be fatal. If this current flows for a longer time, the person in electric shock is being killed.
EFFECTS OF THE ELECTRIC CURRENT ON HUMAN BODY:
^{Current in ampere} |
^{Effect} |
^{0.001} |
^{can be felt} |
^{0.005} |
^{is painful} |
^{0.010} |
^{Causes involuntary muscle contractions (Spasms)} |
^{0.015} |
^{Causes loss of muscle control} |
^{0.070} |
^{If through the heart, causes serious disruption, probably fatal if current laster for more than 1 sec.} |
11. Explain the sign convention used in electric circuit as per Loop's law. (AS 1) 4 Marks
A: i) EMF of the battery is taken as negative when we move from positive terminal to negative terminal across the battery.
ii) It is taken as positive when we move across the battery from negative terminal to positive terminal.
iii) The direction of electric current is to be observed to give a sign to potential difference of a resistor.
iv) The potential difference across the resistor is taken as negative when we move along the direction of electric current through the resistor.
v) It is taken as positive when we move against the direction of electric current through the resistor.
12. Draw the circuit diagrams of all possible combinations with resistors R_{1}, R_{2}, R_{3}, R_{4 } (AS 5) 4 Marks
13. Find the resultant potential difference of the following loops from the given circuit diagram. (AS 4) 4 Marks
i) Loop ABEFA
ii) Loop ACDFA
iii) Loop BCDEB
iv) Loop EFABE
v) Loop DEBCD
vi) Loop DFACD
A: i) For the Loop ABEFA:
The resultant potential difference in the loop ABEFA is
-V_{2} + I_{2}R_{2} - I_{1}R_{1} + V_{1} = 0
ii) For the Loop ACDFA:
The resultant potential difference in the loop ACDFA is
-(I_{1} + I_{2})R_{3} - I_{1}R_{1} + V_{1} = 0
iii) For the Loop BCDEB
The resultant potential difference in the loop BCDEB is
-(I_{1} + I_{2})R_{3} - I_{2}R_{2 }+ V_{2} = 0
iv) For the Loop EFABE:
The resultant potential difference in the loop EFABE is
-I_{1}R_{1} + V_{1} - V_{2} + I_{2}R_{2} = 0
v) For the Loop DEBCD:
The resultant potential difference in the loop DEBCD is
-I_{2}R_{2} + V_{2} - (I_{1} + I_{2})R_{3} = 0
vi) For the Loop DFACD
The resultant potential difference in the loop DFACD is
-I_{1}R_{1} + V_{1} - (I_{1} + I_{2})R_{3} = 0
14. Madhu drew a graph by taking flow of current on Y - axis and voltage on X - axis. He got the values by using a wire, voltmeter and ammeter?
Answer the following questions based on the graph.
i) What kind of wire was it?
ii) Find the resistance of the wire?
iii) How much of electrical energy is used by the wire when a potential difference of 20 V is supplied between the ends of the wire?
iv) Which rule/principle does the above graph show? (AS 4) 4 Marks
A: i) Graph is a straight line. So, the wire is a ohmic conductor (metal)
ii) From graph I = 0.1 A and V = 5 V
From Ohm's law V = IR
^{R =} V/I= %/0.1^{= 50 Ω}
iii) Potential difference between the ends of wire V = 20 V, R = 50 Ω
iv) From above graph V/I is a constant ratio, hence the graph shows Ohm's law.
15. The electric circuit is shown in figure.
Find out the equivalent resistance between A and B? (AS 1) 2 Marks
A: The first three resistors are in parallel.
16. Find the equivalent resistance between the points A and B in the given electric circuit? (AS 1) 2 Marks
A: The voltage divides in three resistors if we connect a battery in between A and B. If we redraw the circuit,
17. Draw the picture which shows the connections of electrical appliances in your home. (AS 5) 2 Marks
A:
18. In household circuits, why do we use fuses?
(OR)
What is the use of fuses? (AS 6) 2 Marks
A: * The fuse consists of a thin wire of low melting point.
* When the current in the fuse exceeds 20 A, the wire will heat up and melt.
* The circuit then becomes open and prevents the flow of current into the household circuit.
* Hence all the electric devices are saved from damage that could be caused by overload.
* Thus we can save the house holding wiring and devices by using fuses.
19. Assume that the resistance of your body is 1,00,000. Ω If you touch a battery of 24 V. Then find the current flowing in your body. What will be the effect of that current on your body? (AS 1) 2 Marks
A: Resistance of the body (R) = 1,00,000 Ω
Potential difference of the battery (V) = 24 V
Current that flows in the body (I) = ?
I = 0.00024 A
This current is very less quantity. When such less quantity current passes through the human body it does not affect the functioning of various organs inside the body.
20. Why doesn't a bird get a shock when it stands on a high voltage wire? (AS 6) 2 Marks
A: There are two parallel transmission lines on electric poles. The potential difference between these two lines is 240 V through out their lengths. If you connect any conducting device across these two wires, it causes current to flow between the wires. When the bird stands on a high voltage wire, there is no potential difference between the legs of the bird. Because it stands on a single wire. So, no current passes through the bird. Hence, it doesn't feel any electric shock.
21. Give reasons for using Lead in making fuses. (AS 1) (AS 6) 2 Marks
A: Lead is used in making fuses. Because it have low melting point. If the current in the Lead wire exceeds certain value the wire will heat up and melts. So, the circuit in households opened and all the electric devices are saved.
22. Draw the symbols of the following.
i) Battery ii) Resistance iii) Ammeter iv) Key (AS 5) 2 marks
23. Draw the shape of V - I graph for a conductor. (AS 5) 1 Mark
24. Draw the shape of V - I graph for a semi conductor. (AS 5) 1 Mark
A: V - I graph for semi conductor:
25. What are the limitations of Ohm's law? (AS 1) 1 Mark
A: Ohm's law is valid for metal conductors, provided the temperature and other physical conditions remain constant.
Ohm's law is not applicable to gaseous conductors.
Ohm's law is not applicable to semi conductors also such as Germanium and Silicon.
26. What are the uses of Semi conductors? (AS 6) 1 Mark
A: Semi conductors are used to make diodes, transistors and integrated circuits (IC's). IC's are used in all sorts of electronic devices, including Computer, TV, Mobile, Phone etc.
27. Which instrument is used to measure electric current? (AS 6) 1 Mark
A: Ammeter
28. Which instrument is used to measure potential difference? (AS 1) 1 Mark
A: Voltmeter
29. Find the value of 'X' in the following figure? (AS 1) 1 Mark
A: From Junction law I_{1} + I_{2} = I_{3} + I_{4}
2 + 5 = 1.5 + x
x = 7 - 1.5
x = 5.5 A
30. Find the resultant potential difference from the given figure based on Loops law. (AS 4) 2 Marks
A: i) For the Loop ABCDA:
The resultant potential difference in the loop is
+V_{1} - IR_{1} + V_{2} - IR_{2} - IR_{3} = 0
ii) For the Loop ADCBA:
The resultant potential difference in the loop is
+IR_{3} + IR_{2} - V_{2} + IR_{1} - V_{1} = 0
PROBLEMS - SOLUTIONS
1. A total charge of 90 coulombs flows in a conductor during a time of 4 minutes. What is the strength of current in the conductor? (AS 1) 2 Marks
Sol: Given Q = 90 Coulombs
t = 4 × 60 = 240 sec
I = ?
^{I =} ^{Q/t}
^{I =} 90/240
= 0.375 Amperes
2. What is the total quantity of charge flows in 5 minutes when a current of 2 amperes exist in a conductor? (AS 1) 2 Marks
Sol: Given I = 2 Amperes
t = 5 × 60 = 300 sec
Q = ?
^{I =} ^{Q/t }
Q = I × t
= 2 × 300
= 600 Coloumbs
3. The potential difference across a bulb is 240 V and a current of 6 A flows through it. Find the resistance of the bulb. (AS 1) 2 Marks
Sol: Given V = 240 V
I = 6 A
R = ?
According to Ohm's Law
^{R = V/I}
^{R =} ^{240/6}
= 40 Ω
4. An immersion heater of resistance 23 Ω is connected to a mains of 230 V supply. How much current flows through it? (AS 1) 2 Marks
Sol: Given R = 23 Ω
V = 230 V
I = ? According to Ohm's Law
^{I =} V/R
^{I =} 230/23
= 10 A
5. 0.15 A current is flowing through a resistance of 10 Ω. What is the potential difference between its ends? (AS 1) 2 Marks
Sol: Given R = 10 Ω
I = 0.15 A V = ?
According to Ohm's Law
V = IR
V = 0.15 × 10
= 1.5 V
6. Assume that the resistance of your body is 5,00,000 Ω and if you touch a 240 V wire, then how much current flows through your body. (AS 1) 2 Marks
Sol: Given R = 5,00,000 Ω
V = 240
I = ?
^{According to Ohm's Law I =} ^{V/R}
^{I =} 240/5,00,000
= 0.00048 A
7. The resistance of a manganin wire of 1 m length is 8 Ω. Find the resistance of a wire of 5 m length of same material having the same area of cross-section. (AS 1) 2 Marks
Sol: Given R_{1} = 8 Ω
l_{1} = 1 m
l_{2} = 5 m
R_{2} = ?
Since R ∝ l, we can write
R_{2} = 40 Ω
8. The resistance of a manganin wire of 1 mm^{2} cross-sectional area is 12 Ω.
Find the resistance of manganin wire of same length. But of a cross-section of 4 mm2. (AS 1) 2 Marks
Sol: Given R1 = 12 Ω
A1 = 1 mm^{2}
A^{2} = 4 mm^{2}
R^{2} = ?
9. The resistance of a brass wire of length 300 m and area of cross-section 3.4 × 10^{-6} m^{2} is 6 Ohms. Find the specific resistance of the material of the wire. (AS 1) 2 Marks
Sol: Given l = 300 m
A = 3.4 × 10^{-6} m^{2}
R = 6 Ω
ρ = ?
Specific resistance
ρ = 6.8 × 10^{-8} Ohm - meter
10. What is the equivalent resistance of two resistors 4 Ω and 8 Ω when connected in (a) series and (b) parallel. (AS 1) 4 Marks
Sol: Given R_{1} = 4 Ω
R_{2} = 8 Ω
(a) When resistance are connected in series the equivalent resistance Req is given by
R_{eq} = R_{1} + R_{2}
R_{eq} = 4 + 8
R_{eq} = 12 Ω
(b) When resistance are connected in parallel the equivalent resistance is given by
11. Calculate the equivalent resistance of two resistors of 1 Ω and 10 Ω connected in parallel. (AS 1) 2 Marks
Sol: Given R_{1} = 1 Ω
R_{2} = 10 Ω
When resistance are connected in parallel the effective resistance R is given by
12. Three resistors 2 Ω, 4 Ω, 8 Ω are connected in (a) series, (b) parallel. Find the resultant resistance in the circuit. (AS 1) 4 Marks
Sol: Given R_{1} = 2 Ω
R_{2} = 4 Ω
R_{3} = 8 Ω
(a) Resultant resistance in series connection
R_{eq} = R_{1} + R_{2} + R_{3}
R_{eq} = 2 + 4 + 8
R_{eq} = 14 Ω
(b) Resultant resistance in parallel connection
13. Three resistors R1 Ω, 2 Ω and 8 Ω are connected in series in a circuit. If the resultant resistance in the circuit is 17 Ω. Find the value of R1. (AS 1) 2 Marks
Sol: Resultant resistance in series connection
Req = R_{1} + R_{2} + R_{3}
17 = R_{1} + 2 + 8
R_{1} = 17 - 10
.^{.}. R_{1} = 7 Ω
14. The effective resistance of a combination of three resistors is 50 Ohms. The value of two resistors are 10 Ω and 15 Ω. Find the value of third resistance? (AS 1) 2 Marks
Sol: Given R_{eq} = 50 Ω
R_{1} = 10 Ω
R_{2} = 15 Ω
R_{3} = ?
Resultant resistance in series connection
R_{eq} = R_{1} + R_{2} + R_{3}
50 = 10 + 15 + R_{3}
R_{3} = 50 - 25
.^{.}. R_{3} = 25 Ω
15. Two resistors are 6 Ω and R2 Ω are connected in parallel in a circuit. If the resultant resistance in the circuit is 4 Ω. Find the value of R2. (AS 1) 2 Marks
Sol: Resultant resistance in parallel connection
R_{2} = 12 Ω
16. Find the resultant resistance in the circuit between A and B from the below diagram.
Sol. Given R_{1} = 3 Ω
R_{2} = 6 Ω
R_{3} = 2 Ω
From the given circuit
R_{1} = 3 Ω, R_{2} = -6 Ω are connected in parallel their resultant resistance is
.^{.}. R_{eq} = 2 Ω
But R_{1}, R_{2} are connected to R_{3} in series their resultant resistance is
R_{eq} = 2 + 2 = 4 Ω
From the above circuit diagram find the effective resistance between X and Y. (AS 1) 4 Marks
Sol. Resistance of I parallel combination is
These three are in series with 1 Ω in between X and Y.
.^{.}. Effective resistance between X and Y is = 1 + 1 + 1 + 1
= 4 Ω
18. It is noted on an electric bulb as 60 W, 240 V. What is the resistance of the filament?
20. A house is fitted with 7 bulbs of each 100 Watt. If each bulb glows for 4 hours a day on an average. Find the cost of consumption in a month of 30 days at Rs.3.00 per unit. (AS 6) 4 Marks
Sol: Electric energy consumed by 7 bulbs at the rate of 4 hours per day for 30 days in kWh.
= 84 kWh or 84 units
Cost of 1 unit = Rs.3.00
Cost of 84 units = 84 × 3.00
= Rs.252.00
SHORT QUESTIONS
1. Name the components required for electric circuit? (AS1) 1 Mark
A: Source (battery), connecting wires, bulb, key (switch).
2. Who proposed that the conductors like metals contains large number of free electrons while the positive ions are fixed in their locations? (AS1) 1 Mark
A: Drude and Lorentz
3. What is the net charge moving along a conductor through any cross section in of it in open circuit? (AS1) 1 Mark
A: Zero
4. In open circuit as shown in figure why do the electrons are arranged randomly? (AS1) 1 Mark
A: As it is not connected to source the electrons are arranged randomly.
5. What are your identifications from the below figure? (AS5) 1 Mark
A: As the electric current is passing in the circuit electrons are arranged in the syestamatic manner.
6. Calculate the drift speed of a electron in a copper wire carrying a current of 1 A and cross sectional area A = 10^{−}^{6} m^{2} and the electron density of copper is n = 8.5 × 10^{28} m^{−}^{3}. (AS1) 2 Marks
7. What is the direction of electric current and direction of motion of electrons in the closed circuit? (AS1) 1 Mark
A: Both electric current and motion of electrons are in opposite direction.
8. What F_{e }indicates in the below diagram? (AS5) 1 Mark
A: Force acting on the charge by electric field.
9. In the electrical circuit how do you measure flow of electric current? (AS1) 1 Mark
A: Ammeter
10. What is the instrument used for measuring potential difference between the two points in the electrical circuit? (AS1) 1 Mark
A: Voltmeter
11. How is Ammeter connected in circuit? (AS1) 1 Mark
A: Series
12. How is Voltmeter connected in circuit? (AS1) 1 Mark
A: Parallel
13. What are you conclusion from the below figure? (AS5) 1 Mark
A: The electric force _{Fe }and chemical force F_{c} that are acting on the ions are balanced in the battery and there will be no motion of ions are concluded from the figure.
14. What is the work done by the chemical force to move unit positive charge from negative terminal to positive terminal of the battery? (AS1) 1 Mark
A: Electro motive force (e.m.f.)
15. Name the components to show the ratio V/I _{ }is a constant for a conductor. (AS3) 1 Mark
A: Dry cells, Conducting wires, Ammeter, Voltmeter, Iron/Manganin spoke, LED and Keys.
16. What should be maintained constant in the experiment to prove ohm's laws? (AS3) 1 Mark
A: Temperature
17. What we call the materials which obeys ohms law and give two examples? (AS1) 1 Mark
A: Ohmic materials
e.g.: Nichrome, Manganin, Iron.
18. What we call the materials which does not obey Ohm's Law? Give two examples? (AS1) 1 Mark
A: Non - ohmic materials
e.g.: LED's, Silicon, Germanium
19. When 0.005 A of current flows in the human body what happens? (AS1) 1 Mark
A: Is painful
20. When 0.070 A of current flows in the human body what happens? (AS1) 1 Mark
A: It effects the heart
21. What is the combined effect of potential difference, electric current and resistance of human body? (AS1) 1 Mark
A: Electric shock
22. What is the potential difference between the two points in the wire which is connected to our house? (AS6) 1 Mark
A: 230 - 240 V
23. In the multimeter display if it reads 1 or displays OL it indicates what? (AS1) 1 Mark
A: Over Load
24. What happens to the resistance when the temperature increases in the conductor? (AS2) 1 Mark
A: Increases
25. What happens to the resistance when the length of the conductor increases? (AS2) 1 Mark
A: Resistance increases
26. What happens to the resistance when the cross Area of the conductor increases? (AS2) 1 Mark
A: Resistance decreases
27. What is the S.I. unit of resistivity? (AS1) 1 Mark
A: Ω - m
28. What is the reciprocal of resistivity? (AS1) 1 Mark
A: Conductivity
29. In real life low resistivity metals are used as? (AS6) 1 Mark
A: Good conductors
e.g.: Copper wire
30. What is the metal used in making filament of the bulb? (AS6) 1 Mark
A: Tungsten.
31. What are the Alloys used as heating element in electrical iron box, toasters etc.,? (AS6) 1 Mark
A: Nichrome and Manganin.
32. What are the metals present in Nichrome? (AS1) 1 Mark
A: Nickel, Chromium and Iron
33. What are the metals present in manganin? (AS1) 1 Mark
A: Copper and Nickel
34. What is used in preparation of Diodes, transistors and integrated circuits (ICS)? (AS6) 1 Mark
A: Semi - conductors
35. Where are the IC's (Integrated Chip) used? (AS6) 1 Mark
A: TV, Computer, Mobile phones, all electronic devices.
36. When the resistors are connected in series? What happens to the resistance of a circuit? (AS1) 1 Mark
A: Increases
37. When the resistors are connected in parallel? What happens to the resistance of a circuit? (AS1) 1 Mark
A: Decreases
38. Find the value of X from the given junction. (AS1) 1 Mark
A: 1.5 + 7 = 2.5 + 1.5 + X
8.5 = 4.0 + X
X = 8.5 − 4.0
X = 4.5
39. From the given figure for the Loop AEDCBA. Find the resultant potential based on the Loop Law. (AS1) 1 Mark
A: +V_{2} - IR_{3} + V_{1} − IR_{3} − IR_{1} = 0
40. What is the unit of the power consumption in houses? (AS6) 1 Mark
A: kWh or unit
41. When does overload of current occur in houses? (AS6) 1 Mark
A: When the current flow reaches above 20 A in the current wires.
42. What happens when the thick wire is taken as fuse wire? (AS2) 2 Marks
A: Its cross - sectional area increases, resistance decreases and current increases. This damages electrical appliances because of over load.
43. Can we use iron wire as fuse? (AS2) 1 Mark
A: No, we can't because it has high melting point.
44. What happens when the electrical appliances in home are connected in series? (AS2) 2 Marks
A: i) All the electrical appliances are to be controlled by a single switch.
ii) If electrical appliances are connected in series. If one of the electrical appliance fails, the remaining electrical appliances will not work.