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 9
A torch uses a 1.5 V cell. Is the current in the torch AC or DC?
Describe one advantage of using AC for long-distance power transmission.
Describe the shape of the graph of current versus time for AC.
Explain why AC is preferred over DC for transmission of electricity over long distances.
A 12 V battery is connected to a 4 Ω resistor. What is the current through the resistor?
A current of 2 A flows through a resistor of 5 Ω. What is the voltage across the resistor?
A device requires 5 A of current at 12 V. What is the power consumed by the device?
A torch uses a 1.5 V cell. Is the current in the torch AC or DC?
Which of the following best describes direct current (DC)?
(1) The current flows in one direction only
(2) The current changes direction periodically
(3) The voltage alternates between positive and negative
(4) The current is always zero
Which of the following devices converts AC to DC?
(1) Transformer
(2) Rectifier
(3) Generator
(4) Motor
Which of the following is a benefit of using AC for household electricity?
(1) It is safer than DC
(2) It is easier to store
(3) It can be easily transformed to different voltages
(4) It is always cheaper
Which of the following is a disadvantage of DC for power transmission?
(1) Difficult to store
(2) Difficult to transform to higher or lower voltages
(3) Causes more energy loss in wires
(4) Cannot be used in electronic devices
Fill in the blank: The current that flows in only one direction is called ______ current.
Fill in the blank: The device that converts mechanical energy into electrical energy is called a ______.
Fill in the blank: The device that stores electrical energy in chemical form and provides DC is called a ______.
Fill in the blank: The device used to increase or decrease AC voltage is called a ______.
True or False: A battery produces alternating current.
True or False: A generator can produce both AC and DC depending on its design.
True or False: AC can be easily converted to DC using a transformer.
True or False: Alternating current (AC) reverses its direction periodically.
