Direct and Alternating Current
Physics ⇒ Electricity and Magnetism
Direct and Alternating Current starts at 9 and continues till grade 12.
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See sample questions for grade 11
A 12 V battery supplies a current of 3 A to a circuit. How much electrical power is being delivered?
A DC circuit has a resistance of 5 Ω and a current of 2 A. What is the voltage across the resistor?
A generator produces an AC voltage described by V(t) = 100 sin(314t). What is the frequency of the AC voltage?
A lamp rated at 60 W, 120 V is connected to a 120 V DC supply. What current does it draw?
A resistor of 10 Ω is connected to an AC source with an RMS voltage of 100 V. What is the RMS current through the resistor?
Describe the function of a commutator in a DC generator.
A generator produces an AC voltage described by V(t) = 100 sin(314t). What is the frequency of the AC voltage?
In a certain country, the AC mains supply is 240 V, 50 Hz. What does 50 Hz represent?
Which device is used to convert AC to DC?
(1) Transformer
(2) Rectifier
(3) Generator
(4) Inductor
Which of the following best describes direct current (DC)?
(1) The current changes direction periodically
(2) The current flows only in one direction
(3) The current has a sinusoidal waveform
(4) The current has zero average value
Which of the following is a disadvantage of DC transmission over long distances?
(1) High energy loss due to resistance
(2) Difficulty in voltage transformation
(3) Both (1) and (2)
(4) None of the above
Which of the following is NOT a source of direct current?
(1) Battery
(2) Solar cell
(3) Dynamo
(4) Transformer
A current described by I(t) = I₀ sin(ωt) is an example of ______ current.
Fill in the blank: The device that increases or decreases the voltage of an alternating current is called a ______.
Fill in the blank: The process of converting AC to DC is called ______.
Fill in the blank: The SI unit of electric current is ______.
State whether the following statement is true or false: The polarity of AC voltage alternates with time.
True or False: Alternating current (AC) reverses its direction periodically.
True or False: The average value of a complete cycle of a pure sinusoidal AC current is zero.
True or False: The direction of current in a DC circuit can change spontaneously without external intervention.
