An alternating current is given by I = I₀ sin πt. Which equation describes a current with twice the frequency and twice the amplitude?
Correct answer A. I = 2I₀ sin(2πt)
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Physics MCQs
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What must be calculated to find the r.m.s. value of an alternating current mathematically?
Correct answer D. Square root of the mean value of I²
An uncharged 30 µF capacitor is charged by a constant current of 10 mA. How long does it take for the potential difference across it to reach 300 V?
Correct answer A. 0.9 s
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What type of waves are the electromagnetic waves radiated by an antenna?
Correct answer A. Transverse
What do electromagnetic waves transport?
Correct answer D. Energy
How is the direction of propagation of an electromagnetic wave related to its fields?
Correct answer C. Perpendicular to both electric and magnetic field
What does a changing magnetic flux induce?
Correct answer C. Electromotive force (emf)
An alternating current with an r.m.s. value of 4.0 A and frequency 50 Hz flows through a 10 Ω resistor. What is the peak current?
Correct answer A. 5.66 A
What is the steady current that produces heat in a resistor at the same rate as the mean heating rate of an alternating current called?
Correct answer A. r.m.s. current
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If the capacitance in an L-C circuit is increased to four times its value, what happens to the frequency?
Correct answer D. One half
What kind of waves are emitted from an antenna?
Correct answer B. Electromagnetic waves
What does an electromagnetic wave consist of?
Correct answer D. Electric and magnetic fields moving perpendicular to each other
Electromagnetic waves in free space travel at the same speed as which of the following?
Correct answer A. γ-rays
What is characteristic of an alternating current or voltage?
Correct answer A. It changes its direction again and again
A moving-coil galvanometer of resistance 100 Ω gives half-scale deflection with a current of 20 mA. What is the potential difference across it?
Correct answer B. 2 V
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What is the effect of heating a magnet?
Correct answer D. It weakens it
A galvanometer is a very sensitive instrument with what kind of damping?
Correct answer B. Very low damping
An electron moving at uniform speed in a vacuum enters a magnetic field at right angles to it. What is its subsequent path?
Correct answer C. A circle in a plane perpendicular to the field
What is an effective way to make a moving coil galvanometer more sensitive?
Correct answer D. Use a very strong magnetic field
How must an ammeter be connected to measure the total current flowing in a circuit?
Correct answer A. In series with the circuit