Physics (School & Undergraduate)

Electrostatics & Circuits Heat & Thermodynamics Mechanics Modern Physics Waves & Optics

Q. If a capacitor is connected to an AC source, what happens to the current through the capacitor?

A. It is constant
B. It leads the voltage
C. It lags the voltage
D. It is zero

Solution

In an AC circuit, the current through a capacitor leads the voltage by 90 degrees.

Correct Answer: B — It leads the voltage

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Q. If a capacitor of 10 µF is charged to 20 V, what is the energy stored in the capacitor?

A. 0.02 J
B. 0.1 J
C. 0.5 J
D. 0.1 mJ

Solution

Energy stored, U = 0.5 * C * V^2 = 0.5 * 10 x 10^-6 F * (20 V)^2 = 0.02 J.

Correct Answer: B — 0.1 J

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Q. If a capacitor of 10 µF is charged to a voltage of 5V, what is the stored energy?

A. 0.125 mJ
B. 0.25 mJ
C. 0.5 mJ
D. 0.75 mJ

Solution

Energy stored U = 0.5 * C * V^2 = 0.5 * 10 x 10^-6 F * (5V)^2 = 0.125 mJ.

Correct Answer: B — 0.25 mJ

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Q. If a capacitor of 10 µF is connected in series with a 20 µF capacitor, what is the total capacitance?

A. 6.67 µF
B. 30 µF
C. 15 µF
D. 8 µF

Solution

1/C_total = 1/C1 + 1/C2 = 1/10 + 1/20 = 3/20, thus C_total = 20/3 µF = 6.67 µF.

Correct Answer: A — 6.67 µF

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Q. If a capacitor of 5 microfarads is charged to 20 volts, what is the energy stored in the capacitor?

A. 0.01 J
B. 0.02 J
C. 0.05 J
D. 0.1 J

Solution

The energy (U) stored in a capacitor is given by U = 0.5 * C * V^2. Here, U = 0.5 * 5 x 10^-6 F * (20^2) = 0.02 J.

Correct Answer: B — 0.02 J

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Q. If a capacitor of 5 µF is charged to 12 V, what is the energy stored in the capacitor?

A. 0.36 mJ
B. 0.72 mJ
C. 1.44 mJ
D. 2.88 mJ

Solution

Energy stored U = 0.5 * C * V^2 = 0.5 * 5 x 10^-6 F * (12 V)^2 = 0.36 mJ.

Correct Answer: A — 0.36 mJ

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Q. If a capacitor of 5 µF is charged to a voltage of 10 V, what is the charge stored in the capacitor?

A. 50 µC
B. 100 µC
C. 25 µC
D. 75 µC

Solution

Charge (Q) = C * V = 5 µF * 10 V = 50 µC.

Correct Answer: A — 50 µC

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Q. If a capacitor of 5 µF is charged to a voltage of 10V, what is the energy stored in the capacitor?

A. 0.25 mJ
B. 0.5 mJ
C. 0.75 mJ
D. 1.0 mJ

Solution

Energy stored, U = 0.5 * C * V² = 0.5 * 5 x 10^-6 F * (10V)² = 0.25 mJ.

Correct Answer: B — 0.5 mJ

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Q. If a capacitor of 5 µF is charged to a voltage of 10V, what is the stored energy?

A. 0.25 mJ
B. 0.5 mJ
C. 0.75 mJ
D. 1 mJ

Solution

Energy stored, U = 0.5 * C * V² = 0.5 * 5 x 10^-6 F * (10V)² = 0.25 mJ.

Correct Answer: B — 0.5 mJ

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Q. If a car accelerates from rest to 20 m/s in 5 seconds, what is its average acceleration?

A. 2 m/s²
B. 4 m/s²
C. 5 m/s²
D. 1 m/s²

Solution

Average acceleration (a) = (final velocity - initial velocity) / time = (20 m/s - 0 m/s) / 5 s = 4 m/s².

Correct Answer: A — 2 m/s²

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Q. If a car accelerates from rest to 20 m/s in 5 seconds, what is the average power output if the car has a mass of 1000 kg?

A. 4000 W
B. 8000 W
C. 16000 W
D. 20000 W

Solution

Work done = Change in Kinetic Energy = 0.5 × 1000 kg × (20 m/s)² = 200000 J. Power = Work / Time = 200000 J / 5 s = 40000 W.

Correct Answer: C — 16000 W

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Q. If a car accelerates from rest to a speed of 20 m/s in 10 seconds, what is the average power output if the car has a mass of 1000 kg?

A. 2000 W
B. 4000 W
C. 6000 W
D. 8000 W

Solution

Work done = Change in Kinetic Energy = 0.5 × 1000 kg × (20 m/s)² = 200000 J. Power = Work / Time = 200000 J / 10 s = 20000 W.

Correct Answer: C — 6000 W

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Q. If a car accelerates from rest to a speed of 20 m/s in 5 seconds, what is its acceleration?

A. 2 m/s²
B. 4 m/s²
C. 5 m/s²
D. 10 m/s²

Solution

Acceleration is calculated using the formula a = (v - u)/t. Here, a = (20 m/s - 0)/5 s = 4 m/s².

Correct Answer: A — 2 m/s²

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Q. If a car is moving at 80 km/h and a cyclist is moving at 20 km/h in the opposite direction, what is the speed of the cyclist relative to the car?

A. 60 km/h
B. 100 km/h
C. 80 km/h
D. 20 km/h

Solution

The speed of the cyclist relative to the car is the sum of their speeds since they are moving in opposite directions: 80 km/h + 20 km/h = 100 km/h.

Correct Answer: B — 100 km/h

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Q. If a car is moving at a constant speed of 60 km/h, how far will it travel in 2 hours?

A. 60 km
B. 120 km
C. 180 km
D. 240 km

Solution

Distance = speed × time = 60 km/h × 2 h = 120 km.

Correct Answer: B — 120 km

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Q. If a car traveling at 20 m/s comes to a stop in 5 seconds, what is its deceleration?

A. 2 m/s²
B. 4 m/s²
C. 5 m/s²
D. 10 m/s²

Solution

Deceleration a = (final velocity - initial velocity) / time = (0 - 20 m/s) / 5 s = -4 m/s².

Correct Answer: B — 4 m/s²

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Q. If a car travels 100 m in 5 seconds, what is its average speed?

A. 20 m/s
B. 25 m/s
C. 15 m/s
D. 30 m/s

Solution

Average speed is calculated as speed = distance/time, so speed = 100 m / 5 s = 20 m/s.

Correct Answer: B — 25 m/s

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Q. If a circuit has a total current of 5 A and a total resistance of 10 Ω, what is the total voltage?

A. 50 V
B. 25 V
C. 10 V
D. 5 V

Solution

Using Ohm's Law, V = I * R = 5 A * 10 Ω = 50 V.

Correct Answer: A — 50 V

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Q. If a circuit has a total resistance of 10 Ω and a current of 2 A, what is the voltage across the circuit?

A. 5 V
B. 10 V
C. 20 V
D. 15 V

Solution

Using Ohm's Law: V = I * R = 2 A * 10 Ω = 20 V.

Correct Answer: C — 20 V

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Q. If a circuit has a total resistance of 10Ω and a current of 5A, what is the voltage across the circuit?

A. 10V
B. 15V
C. 50V
D. 5V

Solution

Using Ohm's Law, V = I * R = 5A * 10Ω = 50V.

Correct Answer: C — 50V

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Q. If a circuit has a total resistance of 10Ω and a total current of 2A, what is the total voltage supplied by the battery?

A. 5V
B. 10V
C. 15V
D. 20V

Solution

Using Ohm's Law, V = I * R = 2A * 10Ω = 20V.

Correct Answer: B — 10V

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Q. If a circuit has a total resistance of 12Ω and a total current of 2A, what is the total voltage supplied by the battery?

A. 12 V
B. 24 V
C. 36 V
D. 48 V

Solution

Using Ohm's law, V = I * R = 2A * 12Ω = 24 V.

Correct Answer: B — 24 V

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Q. If a circuit has a total resistance of 12Ω and a total voltage of 24V, what is the power consumed by the circuit?

A. 48 W
B. 24 W
C. 12 W
D. 36 W

Solution

Power P = V^2 / R = (24V)^2 / 12Ω = 48 W.

Correct Answer: A — 48 W

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Q. If a circuit has a total resistance of 12Ω and a total voltage of 48V, what is the total current in the circuit?

A. 2 A
B. 3 A
C. 4 A
D. 6 A

Solution

Using Ohm's law, I = V/R = 48V / 12Ω = 4 A.

Correct Answer: C — 4 A

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Q. If a circuit has a total resistance of 12Ω and a voltage of 24V, what is the power consumed by the circuit?

A. 48 W
B. 24 W
C. 12 W
D. 36 W

Solution

Power P = V²/R = 24² / 12 = 48 W.

Correct Answer: A — 48 W

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Q. If a circuit has a total voltage of 24 V and a total resistance of 6 Ω, what is the current flowing through the circuit?

A. 2 A
B. 3 A
C. 4 A
D. 5 A

Solution

Using Ohm's law, I = V/R = 24 V / 6 Ω = 4 A.

Correct Answer: B — 3 A

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Q. If a circuit has a total voltage of 24V and a total resistance of 8Ω, what is the power consumed?

A. 72 W
B. 48 W
C. 36 W
D. 24 W

Solution

Power P = V^2 / R = 24V^2 / 8Ω = 72 W.

Correct Answer: A — 72 W

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Q. If a circuit has a voltage of 12 V and a resistance of 4 Ω, what is the current flowing through the circuit?

A. 3 A
B. 4 A
C. 2 A
D. 6 A

Solution

Using Ohm's Law, I = V/R = 12 V / 4 Ω = 3 A.

Correct Answer: A — 3 A

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Q. If a conductor moves perpendicular to a magnetic field, what is the induced emf proportional to?

A. Speed of the conductor
B. Angle of movement
C. Length of the conductor
D. Both speed and length

Solution

The induced emf is proportional to both the speed of the conductor and the length of the conductor when moving perpendicular to the magnetic field.

Correct Answer: D — Both speed and length

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Q. If a dielectric material with a dielectric constant of 4 is inserted into a capacitor, how does the capacitance change?

A. It doubles
B. It quadruples
C. It halves
D. It remains the same

Solution

The capacitance increases by a factor equal to the dielectric constant. Thus, it quadruples.

Correct Answer: B — It quadruples

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Physics (School & Undergraduate)

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