Current Electricity
Q. In a potentiometer, if the length of the wire is 20 m and the potential difference is 10 V, what is the voltage drop per meter?
A.
0.5 V/m
B.
1 V/m
C.
2 V/m
D.
5 V/m
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Solution
The voltage drop per meter is calculated as V/L = 10 V / 20 m = 0.5 V/m.
Correct Answer: B — 1 V/m
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Q. In a potentiometer, if the wire has a uniform cross-section, how does it affect the potential gradient?
A.
It becomes non-uniform
B.
It remains uniform
C.
It increases
D.
It decreases
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Solution
If the wire has a uniform cross-section, the potential gradient remains uniform along its length.
Correct Answer: B — It remains uniform
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Q. In a potentiometer, if the wire is made of a material with higher resistivity, what effect does it have on the potential gradient?
A.
It increases the potential gradient.
B.
It decreases the potential gradient.
C.
It has no effect.
D.
It makes the potentiometer unusable.
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Solution
Higher resistivity increases the resistance of the wire, which decreases the current for a given voltage, thus increasing the potential gradient.
Correct Answer: B — It decreases the potential gradient.
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Q. In a potentiometer, what is the role of the jockey?
A.
To measure current.
B.
To connect the circuit.
C.
To find the balance point.
D.
To provide a reference voltage.
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Solution
The jockey is used to find the balance point where the potential difference is equal to the reference voltage.
Correct Answer: C — To find the balance point.
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Q. In a practical Wheatstone bridge, what is the effect of temperature on resistance measurements?
A.
Temperature has no effect
B.
Resistance increases with temperature
C.
Resistance decreases with temperature
D.
It depends on the material
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Solution
The effect of temperature on resistance measurements in a Wheatstone bridge depends on the material of the resistors, as different materials have different temperature coefficients.
Correct Answer: D — It depends on the material
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Q. In a practical Wheatstone bridge, what is the effect of temperature on the resistances?
A.
Resistances remain constant
B.
Resistances increase with temperature
C.
Resistances decrease with temperature
D.
Temperature has no effect
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Solution
In general, the resistance of conductors increases with temperature due to increased atomic vibrations.
Correct Answer: B — Resistances increase with temperature
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Q. In a practical Wheatstone bridge, what is the effect of temperature on the resistors?
A.
It has no effect
B.
It can change resistance values
C.
It only affects the galvanometer
D.
It only affects the power supply
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Solution
Temperature changes can affect the resistance values of the resistors, thus affecting the balance condition.
Correct Answer: B — It can change resistance values
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Q. In a practical Wheatstone bridge, what is the main source of error?
A.
Temperature variations
B.
Resistance of the connecting wires
C.
Calibration of the galvanometer
D.
Non-ideal resistors
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Solution
Non-ideal resistors can introduce errors in the measurements due to their tolerance and temperature coefficients.
Correct Answer: D — Non-ideal resistors
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Q. In a series circuit with a 12V battery and three resistors of 2Ω, 3Ω, and 5Ω, what is the current flowing through the circuit?
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Solution
Total resistance R = 2Ω + 3Ω + 5Ω = 10Ω. Current I = V / R = 12V / 10Ω = 1.2A.
Correct Answer: B — 2A
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Q. In a series circuit with a 12V battery and two resistors of 3Ω and 6Ω, what is the current flowing through the circuit?
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Solution
Total resistance R = R1 + R2 = 3Ω + 6Ω = 9Ω. Current I = V/R = 12V/9Ω = 4/3A.
Correct Answer: B — 2A
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Q. In a series circuit with a 12V battery and two resistors of 4Ω and 8Ω, what is the current flowing through the circuit?
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Solution
Total resistance R = R1 + R2 = 4Ω + 8Ω = 12Ω; I = V / R = 12V / 12Ω = 1A.
Correct Answer: B — 2A
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Q. In a series circuit, if one resistor fails (opens), what happens to the current in the circuit?
A.
It increases
B.
It decreases
C.
It becomes zero
D.
It remains the same
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Solution
In a series circuit, if one resistor fails, the circuit is broken and the current becomes zero.
Correct Answer: C — It becomes zero
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Q. In a series circuit, if one resistor fails open, what happens to the current in the circuit?
A.
It increases
B.
It decreases
C.
It becomes zero
D.
It remains the same
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Solution
In a series circuit, if one resistor fails open, the current becomes zero because the circuit is broken.
Correct Answer: C — It becomes zero
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Q. In a series circuit, if one resistor has a resistance of 5 Ω and another has 10 Ω, what is the total resistance?
A.
5 Ω
B.
10 Ω
C.
15 Ω
D.
20 Ω
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Solution
In a series circuit, total resistance R_total = R1 + R2 = 5 Ω + 10 Ω = 15 Ω.
Correct Answer: C — 15 Ω
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Q. In a series circuit, if one resistor has a resistivity of 5 Ω·m and another has 10 Ω·m, what is the total resistance?
A.
5 Ω
B.
10 Ω
C.
15 Ω
D.
20 Ω
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Solution
In series, total resistance R_total = R1 + R2 = 5 + 10 = 15 Ω.
Correct Answer: C — 15 Ω
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Q. In a series circuit, if one resistor is removed, what happens to the total resistance?
A.
It increases.
B.
It decreases.
C.
It remains the same.
D.
It becomes zero.
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Solution
In a series circuit, removing a resistor decreases the total resistance because the total resistance is the sum of all resistances.
Correct Answer: B — It decreases.
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Q. In a temperature-resistivity graph, what does the slope represent for a metallic conductor?
A.
Resistivity
B.
Temperature coefficient of resistivity
C.
Resistance
D.
Conductivity
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Solution
The slope of the temperature-resistivity graph represents the temperature coefficient of resistivity.
Correct Answer: B — Temperature coefficient of resistivity
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Q. In a Wheatstone bridge, if all resistances are equal, what is the condition for balance?
A.
Any configuration.
B.
R1 = R2 = R3 = R4.
C.
R1 + R2 = R3 + R4.
D.
R1/R2 = R3/R4.
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Solution
When all resistances are equal, the bridge is balanced regardless of the configuration.
Correct Answer: B — R1 = R2 = R3 = R4.
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Q. In a Wheatstone bridge, if one of the resistors is changed, how does it affect the balance condition?
A.
It does not affect the balance
B.
It always unbalances the bridge
C.
It can either balance or unbalance the bridge
D.
It only balances if the new resistor is equal
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Solution
Changing one resistor can either balance or unbalance the bridge depending on the new value relative to the others.
Correct Answer: C — It can either balance or unbalance the bridge
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Q. In a Wheatstone bridge, if P = 20Ω, Q = 30Ω, and R = 10Ω, what is the value of S for the bridge to be balanced?
A.
15Ω
B.
20Ω
C.
25Ω
D.
30Ω
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Solution
Using the balance condition P/Q = R/S, we find S = 15Ω.
Correct Answer: B — 20Ω
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Q. In a Wheatstone bridge, if R1 = 10Ω, R2 = 15Ω, and R3 = 30Ω, what is the value of R4 for the bridge to be balanced?
A.
20Ω
B.
25Ω
C.
30Ω
D.
35Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (15 * 30) / 10 = 45Ω.
Correct Answer: B — 25Ω
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Q. In a Wheatstone bridge, if R1 = 10Ω, R2 = 20Ω, and R3 = 30Ω, what is the value of R4 for the bridge to be balanced?
A.
15Ω
B.
20Ω
C.
25Ω
D.
30Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we have 10/20 = 30/R4, which gives R4 = 20Ω.
Correct Answer: B — 20Ω
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Q. In a Wheatstone bridge, if R1 = 10Ω, R2 = 20Ω, R3 = 15Ω, what should R4 be for the bridge to be balanced?
A.
30Ω
B.
20Ω
C.
15Ω
D.
10Ω
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Solution
For balance, R1/R2 = R3/R4. Thus, 10/20 = 15/R4, giving R4 = 30Ω.
Correct Answer: B — 20Ω
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Q. In a Wheatstone bridge, if R1 = 1Ω, R2 = 2Ω, and R3 = 3Ω, what is the value of R4 for the bridge to be balanced?
A.
1.5Ω
B.
2Ω
C.
3Ω
D.
4Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we have 1/2 = 3/R4. Solving gives R4 = 6Ω.
Correct Answer: D — 4Ω
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Q. In a Wheatstone bridge, if R1 = 20Ω, R2 = 30Ω, and R3 = 10Ω, what is the value of R4 for balance?
A.
15Ω
B.
20Ω
C.
25Ω
D.
30Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (30 * 10) / 20 = 15Ω.
Correct Answer: B — 20Ω
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Q. In a Wheatstone bridge, if R1 = 20Ω, R2 = 30Ω, and R3 = 10Ω, what is the value of R4 for the bridge to be balanced?
A.
15Ω
B.
20Ω
C.
25Ω
D.
30Ω
Show solution
Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (30 * 10) / 20 = 15Ω.
Correct Answer: B — 20Ω
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Q. In a Wheatstone bridge, if R1 = 2Ω, R2 = 3Ω, and R3 = 6Ω, what is the value of R4 for balance?
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (3 * 6) / 2 = 9Ω.
Correct Answer: C — 6Ω
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Q. In a Wheatstone bridge, if R1 = 2Ω, R2 = 3Ω, and R3 = 6Ω, what is the value of R4 for the bridge to be balanced?
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (3 * 6) / 2 = 9Ω.
Correct Answer: C — 12Ω
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Q. In a Wheatstone bridge, if R1 = 3Ω, R2 = 6Ω, and R3 = 9Ω, what is the value of R4 for balance?
A.
4.5Ω
B.
6Ω
C.
9Ω
D.
12Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = 6Ω.
Correct Answer: B — 6Ω
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Q. In a Wheatstone bridge, if R1 = 4Ω, R2 = 6Ω, and R3 = 12Ω, what is the value of R4 for the bridge to be balanced?
A.
8Ω
B.
9Ω
C.
10Ω
D.
12Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (6 * 12) / 4 = 18Ω.
Correct Answer: D — 12Ω
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