Current Electricity
Q. If the temperature of a metallic conductor increases, what happens to its resistivity?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
For metals, resistivity increases with temperature due to increased lattice vibrations.
Correct Answer: A — Increases
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Q. If the total resistance in a Wheatstone bridge is 30Ω and the bridge is balanced, what is the current through the galvanometer?
A.
0A
B.
1A
C.
2A
D.
Depends on the voltage
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Solution
In a balanced Wheatstone bridge, the current through the galvanometer is zero.
Correct Answer: A — 0A
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Q. If the total resistance in a Wheatstone bridge is increased, what happens to the current in the circuit?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
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Solution
According to Ohm's law, if the total resistance increases, the current in the circuit decreases.
Correct Answer: B — It decreases
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Q. If the value of one of the resistances in a Wheatstone bridge is doubled, what effect does it have on the balance condition?
A.
It remains balanced
B.
It becomes unbalanced
C.
It depends on other resistances
D.
It cannot be determined
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Solution
Doubling one resistance will change the ratio, thus making the bridge unbalanced.
Correct Answer: B — It becomes unbalanced
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Q. If the value of one of the resistances in a Wheatstone bridge is increased, what effect does it have on the balance of the bridge?
A.
It remains balanced
B.
It becomes unbalanced
C.
It depends on the other resistances
D.
It becomes short-circuited
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Solution
Increasing one resistance will generally cause the bridge to become unbalanced.
Correct Answer: B — It becomes unbalanced
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Q. If the voltage across a conductor is 15 volts and the current is 3 amperes, what is the resistance?
A.
5 Ω
B.
10 Ω
C.
15 Ω
D.
20 Ω
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Solution
Using Ohm's Law, R = V / I = 15 V / 3 A = 5 Ω.
Correct Answer: A — 5 Ω
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Q. If the voltage across a resistor is doubled, what happens to the current through it?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, if voltage is doubled and resistance remains constant, current also doubles.
Correct Answer: A — It doubles
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Q. If the voltage across a resistor is doubled, what happens to the current through the resistor, assuming resistance remains constant?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases by a factor of four
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Solution
According to Ohm's Law (V = IR), if voltage is doubled and resistance remains constant, current also doubles.
Correct Answer: A — Doubles
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Q. If the voltage across a resistor is tripled, what happens to the current through it, assuming resistance remains constant?
A.
It triples.
B.
It doubles.
C.
It remains the same.
D.
It decreases.
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Solution
According to Ohm's Law (I = V/R), if voltage (V) is tripled and resistance (R) remains constant, the current (I) will also triple.
Correct Answer: A — It triples.
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Q. If the Wheatstone bridge is balanced, what is the potential difference across the galvanometer?
A.
Maximum.
B.
Minimum.
C.
Zero.
D.
Equal to the supply voltage.
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Solution
When the bridge is balanced, the potential difference across the galvanometer is zero.
Correct Answer: C — Zero.
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Q. If the Wheatstone bridge is unbalanced, what can be inferred about the potential difference across the galvanometer?
A.
It is zero
B.
It is positive
C.
It is negative
D.
It is non-zero
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Solution
An unbalanced Wheatstone bridge will have a non-zero potential difference across the galvanometer.
Correct Answer: D — It is non-zero
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Q. If the Wheatstone bridge is unbalanced, what can be inferred about the resistances?
A.
R1/R2 = R3/R4
B.
R1/R2 ≠ R3/R4
C.
R1 + R2 = R3 + R4
D.
R1 - R2 = R3 - R4
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Solution
An unbalanced Wheatstone bridge indicates that the ratio of the resistances is not equal.
Correct Answer: B — R1/R2 ≠ R3/R4
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Q. If the Wheatstone bridge is unbalanced, what can be said about the potential difference across the galvanometer?
A.
It is zero.
B.
It is maximum.
C.
It is equal to the supply voltage.
D.
It is constant.
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Solution
In an unbalanced bridge, there is a potential difference across the galvanometer, leading to maximum current flow.
Correct Answer: B — It is maximum.
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Q. If the Wheatstone bridge is unbalanced, what happens to the current through the galvanometer?
A.
It becomes zero.
B.
It increases.
C.
It decreases.
D.
It becomes infinite.
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Solution
In an unbalanced bridge, there is a potential difference across the galvanometer, causing current to flow.
Correct Answer: B — It increases.
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Q. If two resistors of 4 ohms and 6 ohms are connected in parallel, what is the current through the 4 ohm resistor when a 12V battery is connected?
A.
3 A
B.
2 A
C.
1 A
D.
4 A
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Solution
Using Ohm's law, I = V/R, for the 4 ohm resistor, I = 12V / 4 ohms = 3 A.
Correct Answer: A — 3 A
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Q. If two resistors of 4 ohms and 6 ohms are connected in series, what is the voltage drop across the 4 ohm resistor when a current of 2 A flows through the circuit?
A.
8 V
B.
4 V
C.
2 V
D.
6 V
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Solution
Using Ohm's law, V = I * R, the voltage drop across the 4 ohm resistor is V = 2 A * 4 ohms = 8 V.
Correct Answer: A — 8 V
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Q. If two resistors of resistivity 5 x 10^-6 Ω·m are connected in series, what is the total resistivity?
A.
5 x 10^-6 Ω·m
B.
10 x 10^-6 Ω·m
C.
2.5 x 10^-6 Ω·m
D.
None of the above
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Solution
Resistivity is a property of the material, not the configuration; it remains 5 x 10^-6 Ω·m.
Correct Answer: A — 5 x 10^-6 Ω·m
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Q. If two resistors of resistivity 5 Ω·m and 10 Ω·m are connected in series, what is the total resistance?
A.
15 Ω
B.
5 Ω
C.
10 Ω
D.
20 Ω
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Solution
Total resistance in series is the sum: R_total = R1 + R2 = 5 + 10 = 15 Ω.
Correct Answer: A — 15 Ω
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Q. If two resistors of resistivity ρ are connected in series, what is the total resistivity of the combination?
A.
ρ
B.
2ρ
C.
ρ/2
D.
Depends on the configuration
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Solution
Resistivity is a property of the material and does not change with series or parallel connections.
Correct Answer: A — ρ
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Q. If two wires of the same material are connected in series, how does their combined resistance compare to the individual resistances?
A.
Less than both
B.
Equal to the sum
C.
Greater than both
D.
Depends on length
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Solution
In series, the total resistance is the sum of individual resistances.
Correct Answer: B — Equal to the sum
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Q. In a balanced Wheatstone bridge, if R1 = 10Ω, R2 = 15Ω, and R3 = 5Ω, what is the value of R4?
A.
7.5Ω
B.
10Ω
C.
15Ω
D.
20Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (15 * 5) / 10 = 7.5Ω.
Correct Answer: A — 7.5Ω
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Q. In a balanced Wheatstone bridge, if R1 = 10Ω, R2 = 5Ω, and R3 = 15Ω, what is the value of R4?
A.
7.5Ω
B.
10Ω
C.
12.5Ω
D.
20Ω
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Solution
Using the balance condition R1/R2 = R3/R4, we find R4 = (R2 * R3) / R1 = (5 * 15) / 10 = 7.5Ω.
Correct Answer: C — 12.5Ω
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Q. In a balanced Wheatstone bridge, the potential difference across the galvanometer is:
A.
Equal to the supply voltage.
B.
Zero.
C.
Equal to the resistance of the galvanometer.
D.
Equal to the potential difference across R1.
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Solution
In a balanced Wheatstone bridge, the potential difference across the galvanometer is zero.
Correct Answer: B — Zero.
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Q. In a balanced Wheatstone bridge, what is the potential difference across the galvanometer?
A.
Equal to the supply voltage
B.
Zero
C.
Equal to the resistance
D.
Depends on the resistances
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Solution
In a balanced Wheatstone bridge, the potential difference across the galvanometer is zero.
Correct Answer: B — Zero
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Q. In a balanced Wheatstone bridge, what is the relationship between the resistances R1, R2, R3, and R4?
A.
R1/R2 = R3/R4
B.
R1 + R2 = R3 + R4
C.
R1 * R4 = R2 * R3
D.
R1 - R2 = R3 - R4
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Solution
In a balanced Wheatstone bridge, the ratio of the resistances in one arm equals the ratio in the other arm, hence R1/R2 = R3/R4.
Correct Answer: A — R1/R2 = R3/R4
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Q. In a circuit with a 10V battery and two resistors (3Ω and 6Ω) in series, what is the voltage drop across the 6Ω resistor?
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Solution
Voltage drop across R2 = (R2 / (R1 + R2)) * Vtotal = (6 / (3 + 6)) * 10 = 6.67V.
Correct Answer: C — 6V
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Q. In a circuit with a 10V battery and two resistors in parallel (4Ω and 6Ω), what is the voltage across each resistor?
A.
10V for both
B.
5V for both
C.
10V for 4Ω and 6V for 6Ω
D.
10V for 6Ω and 4V for 4Ω
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Solution
In a parallel circuit, the voltage across each resistor is the same as the source voltage. Therefore, both resistors have 10V across them.
Correct Answer: A — 10V for both
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Q. In a circuit with a 10V battery and two resistors in series (2Ω and 3Ω), what is the voltage drop across the 3Ω resistor?
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Solution
Using the voltage divider rule, V3 = (R3 / (R2 + R3)) * Vtotal = (3 / (2 + 3)) * 10 = 6V.
Correct Answer: B — 6V
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Q. In a circuit with a 10V battery and two resistors in series (R1 = 2Ω, R2 = 3Ω), what is the current flowing through the circuit?
A.
2A
B.
1A
C.
0.5A
D.
3A
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Solution
Total resistance R_total = R1 + R2 = 2Ω + 3Ω = 5Ω. Current I = V / R_total = 10V / 5Ω = 2A.
Correct Answer: B — 1A
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Q. In a circuit with a 10V battery and two resistors in series (R1 = 2Ω, R2 = 8Ω), what is the current flowing through the circuit?
A.
0.5A
B.
1A
C.
2A
D.
5A
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Solution
Total resistance R_total = R1 + R2 = 2Ω + 8Ω = 10Ω. Current I = V/R = 10V/10Ω = 1A.
Correct Answer: B — 1A
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