A capacitor draws 0.50 A from a 50 Hz supply. The frequency is changed to 100 Hz with the same rms voltage. What current does it now draw?
Correct answer C. 1.0 A
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MDCAT ECAT Physics MCQs
Page 8 of MDCAT ECAT Physics multiple-choice questions with answers. Tap an option to check yourself.
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- Electromagnetic Induction 30
- Fluid Dynamics 30
- Electrostatics 30
- Electronics 30
- Electromagnetism 30
- Current Electricity 30
- Work and Energy 30
- Waves 30
- Vectors and Equilibrium 30
- Nuclear Physics 30
- Dawn of Modern Physics 30
- Thermodynamics 30
- Rotational and Circular Motion 30
- Atomic Spectra 30
- Alternating Current 30
- Force and Motion 30
What is the phase relationship between the alternating current and the voltage across a pure resistor?
Correct answer B. They are in phase
In a purely inductive AC circuit, how does the current compare in phase with the applied voltage?
Correct answer D. Current lags voltage by 90°
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In a purely capacitive AC circuit, how does the current compare in phase with the applied voltage?
Correct answer C. Current leads voltage by 90°
How does the reactance of a capacitor change as the frequency of the AC supply increases?
Correct answer C. It decreases
How does the reactance of an inductor depend on the frequency of the AC supply?
Correct answer A. It is directly proportional to frequency
What is the average power consumed by a pure inductor connected to an AC supply over a complete cycle?
Correct answer A. Zero
What is the reactance of a 0.20 H inductor on a 50 Hz supply?
Correct answer C. 62.8 Ω
What is the reactance of a 10 μF capacitor on a 50 Hz supply?
Correct answer A. 318 Ω
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An AC supply has a peak voltage of 325 V. What is its rms voltage?
Correct answer A. 230 V
How is flux leakage minimised in a practical transformer?
Correct answer B. By winding the coils close together on a closed soft-iron core
Two coils have a mutual inductance of 0.20 H. The current in the first coil changes at 50 A/s. What emf is induced in the second coil?
Correct answer B. 10 V
Which of the following is equivalent to the henry, the unit of inductance?
Correct answer B. V s A⁻¹
Which application makes use of eddy currents to produce a braking force?
Correct answer B. Electromagnetic braking in trains
The flux through each turn of a 100-turn coil changes by 4.0 mWb, producing an average emf of 2.0 V. How long did the change take?
Correct answer C. 0.20 s
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A transformer with 1200 primary turns steps 230 V down to 11.5 V. How many turns are on its secondary?
Correct answer A. 60
The number of turns in a coil is doubled, and the rate of change of flux through each turn is halved. How does the induced emf change?
Correct answer A. It stays the same
Why is soft iron preferred to steel for the core of a transformer?
Correct answer D. It is easily magnetised and demagnetised, so hysteresis loss is small
An ideal transformer has 500 turns on its primary and 2500 turns on its secondary. If the primary is connected to 230 V AC, what is the secondary voltage?
Correct answer D. 1150 V
An ideal transformer steps 240 V down to 12 V. When the secondary current is 2.0 A, what is the primary current?
Correct answer D. 0.10 A