Current Electricity
Q. What is the unit of resistance in the SI system?
A.
Volt
B.
Ampere
C.
Ohm
D.
Watt
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Solution
The unit of resistance in the SI system is the Ohm (Ω).
Correct Answer: C — Ohm
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Q. What is the unit of resistance?
A.
Volt
B.
Ampere
C.
Ohm
D.
Watt
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Solution
The unit of resistance is Ohm, which is defined as the resistance between two points when a constant potential difference of one volt produces a current of one ampere.
Correct Answer: C — Ohm
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Q. What is the unit of resistivity?
A.
Ohm
B.
Ohm-meter
C.
Siemens
D.
Coulomb
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Solution
The unit of resistivity is Ohm-meter (Ω·m).
Correct Answer: B — Ohm-meter
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Q. What is the voltage across a 10 ohm resistor carrying a current of 0.5 A?
A.
5 V
B.
10 V
C.
15 V
D.
20 V
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Solution
Using Ohm's law, V = I * R = 0.5 A * 10 Ω = 5 V.
Correct Answer: A — 5 V
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Q. What is the voltage drop across a 3 ohm resistor carrying a current of 2 A?
A.
3 V
B.
6 V
C.
9 V
D.
12 V
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Solution
Using Ohm's law, V = I * R = 2 A * 3 ohms = 6 V.
Correct Answer: B — 6 V
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Q. What is the voltage drop across a 5 ohm resistor carrying a current of 2 A?
A.
5 V
B.
10 V
C.
15 V
D.
20 V
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Solution
Using Ohm's law, V = I * R = 2 A * 5 ohms = 10 V.
Correct Answer: B — 10 V
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Q. What is the voltage drop across a 5 ohm resistor carrying a current of 3 A?
A.
15 V
B.
10 V
C.
5 V
D.
20 V
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Solution
Using Ohm's law, V = I * R = 3 A * 5Ω = 15 V.
Correct Answer: A — 15 V
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Q. What is the voltage drop across a 5Ω resistor carrying a current of 3A?
A.
5V
B.
10V
C.
15V
D.
20V
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Solution
Using Ohm's law, V = I * R = 3A * 5Ω = 15V.
Correct Answer: C — 15V
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Q. What type of circuit is a potentiometer typically used in?
A.
Series circuit
B.
Parallel circuit
C.
Open circuit
D.
Closed circuit
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Solution
A potentiometer is typically used in a closed circuit to measure voltage without drawing current.
Correct Answer: D — Closed circuit
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Q. What type of circuit is typically used in a potentiometer setup?
A.
Series circuit
B.
Parallel circuit
C.
Combination circuit
D.
Open circuit
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Solution
A potentiometer setup typically uses a series circuit to ensure a constant current flows through the wire.
Correct Answer: A — Series circuit
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Q. When using a potentiometer to measure an unknown voltage, the balance point is found at 4 m. If the known voltage is 12 V, what is the unknown voltage?
A.
6 V
B.
8 V
C.
12 V
D.
16 V
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Solution
Using the formula Vx/Vk = Lx/Lk, we have Vx = Vk * (Lx/Lk). Here, Lx = 4 m, Lk = 10 m, Vk = 12 V, thus Vx = 12 V * (4/10) = 4.8 V.
Correct Answer: C — 12 V
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Q. When using a potentiometer to measure an unknown voltage, what is the condition for balance?
A.
The current through the potentiometer must be maximum
B.
The potential difference across the galvanometer must be zero
C.
The resistance of the potentiometer must be zero
D.
The length of the wire must be equal to the unknown voltage
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Solution
The condition for balance in a potentiometer is that the potential difference across the galvanometer must be zero, indicating that the unknown voltage is equal to the voltage across the potentiometer wire.
Correct Answer: B — The potential difference across the galvanometer must be zero
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Q. When using a potentiometer to measure the emf of a cell, what condition must be satisfied?
A.
The circuit must be closed
B.
The circuit must be open
C.
The cell must be short-circuited
D.
The cell must be connected in series
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Solution
The circuit must be open when measuring the emf of a cell with a potentiometer to ensure that no current flows through the cell, allowing for an accurate measurement.
Correct Answer: B — The circuit must be open
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Q. When using a potentiometer to measure the emf of a cell, what is the condition for balance?
A.
The current through the potentiometer must be maximum.
B.
The potential difference across the cell must equal the potential drop across the wire.
C.
The resistance of the potentiometer must be zero.
D.
The length of the wire must be zero.
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Solution
At balance, the potential difference across the cell equals the potential drop across the potentiometer wire.
Correct Answer: B — The potential difference across the cell must equal the potential drop across the wire.
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Q. When using a potentiometer, why is it important to keep the circuit closed while taking measurements?
A.
To prevent short circuits
B.
To ensure accurate voltage readings
C.
To avoid overheating
D.
To maintain constant current
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Solution
Keeping the circuit closed ensures that the current flows properly, allowing for accurate voltage measurements.
Correct Answer: B — To ensure accurate voltage readings
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Q. Which material has the highest resistivity?
A.
Copper
B.
Aluminum
C.
Iron
D.
Rubber
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Solution
Rubber has a much higher resistivity compared to metals like copper, aluminum, and iron.
Correct Answer: D — Rubber
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Q. Which material has the lowest resistivity?
A.
Copper
B.
Aluminum
C.
Silver
D.
Iron
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Solution
Silver has the lowest resistivity among common materials.
Correct Answer: C — Silver
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Q. Which of the following configurations can be used to create a Wheatstone bridge?
A.
Series only
B.
Parallel only
C.
Series and parallel
D.
None of the above
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Solution
A Wheatstone bridge can be formed using a combination of series and parallel resistors.
Correct Answer: C — Series and parallel
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Q. Which of the following factors does NOT affect the accuracy of a potentiometer?
A.
Temperature
B.
Length of the wire
C.
Material of the wire
D.
Color of the wire
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Solution
The color of the wire does not affect the accuracy of a potentiometer; however, temperature, length, and material do.
Correct Answer: D — Color of the wire
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Q. Which of the following factors does NOT affect the resistivity of a material?
A.
Temperature
B.
Material type
C.
Length of the conductor
D.
Cross-sectional area
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Solution
Resistivity is a property of the material and does not depend on the length or cross-sectional area.
Correct Answer: C — Length of the conductor
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Q. Which of the following is NOT a component of a Wheatstone bridge?
A.
Galvanometer
B.
Battery
C.
Inductor
D.
Resistors
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Solution
An inductor is not a component of a Wheatstone bridge; it consists of resistors, a galvanometer, and a battery.
Correct Answer: C — Inductor
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Q. Which of the following is NOT a condition for a Wheatstone bridge to be balanced?
A.
The ratio of resistances must be equal
B.
No current flows through the galvanometer
C.
The resistances must be equal
D.
The potential difference across the galvanometer is zero
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Solution
While the other conditions are necessary for balance, the resistances do not need to be equal, just in the same ratio.
Correct Answer: C — The resistances must be equal
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Q. Which of the following is NOT a practical application of a Wheatstone bridge?
A.
Measuring small resistances
B.
Calibration of measuring instruments
C.
Determining the specific resistance of a material
D.
Generating high voltages
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Solution
A Wheatstone bridge is not used for generating high voltages; it is used for measuring resistances.
Correct Answer: D — Generating high voltages
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Q. Which of the following is NOT a practical application of the Wheatstone bridge?
A.
Measuring unknown resistances
B.
Calibration of measuring instruments
C.
Determining the specific heat of a substance
D.
Testing electrical components
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Solution
Determining the specific heat of a substance is not a practical application of the Wheatstone bridge.
Correct Answer: C — Determining the specific heat of a substance
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Q. Which of the following is NOT a use of a potentiometer?
A.
Measuring emf of a cell.
B.
Comparing emf of two cells.
C.
Measuring resistance directly.
D.
Calibrating voltmeters.
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Solution
A potentiometer is not used for direct resistance measurement; it is primarily used for voltage measurements.
Correct Answer: C — Measuring resistance directly.
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Q. Which of the following materials has the highest resistivity?
A.
Copper
B.
Aluminum
C.
Silver
D.
Rubber
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Solution
Rubber is an insulator and has a much higher resistivity compared to metals like copper, aluminum, and silver.
Correct Answer: D — Rubber
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Q. Which of the following materials is commonly used for potentiometer wires?
A.
Copper
B.
Aluminum
C.
Constantan
D.
Silver
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Solution
Constantan is commonly used for potentiometer wires due to its stable resistance over a range of temperatures.
Correct Answer: C — Constantan
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Q. Which of the following materials is commonly used for the wire in a potentiometer?
A.
Copper
B.
Aluminum
C.
Constantan
D.
Silver
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Solution
Constantan is commonly used for potentiometer wires due to its stable resistance over a range of temperatures.
Correct Answer: C — Constantan
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Q. Which of the following materials is typically a good conductor of electricity?
A.
Rubber
B.
Copper
C.
Glass
D.
Wood
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Solution
Copper is a good conductor of electricity, while rubber, glass, and wood are insulators.
Correct Answer: B — Copper
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Q. Which of the following statements about a potentiometer is true?
A.
It can only measure AC voltages.
B.
It requires a constant current for accurate measurements.
C.
It can measure both AC and DC voltages.
D.
It is only used in laboratory settings.
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Solution
A potentiometer requires a constant current to ensure accurate measurements of voltage.
Correct Answer: B — It requires a constant current for accurate measurements.
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