alleryStart learning →A heater wire carries a steady 3 A for 10 s. What total charge moves through it?
- 3.3 C
- 30 C
- 0.3 C
- 13 C
Show answer and solution
Correct answer: B. 30 C
Charge equals current times time, so 3 A for 10 s moves 30 coulombs.
Olympiad (Class 7) Electric current and its effects — practice questions
Explore 65 free Electric current and its effects questions in Olympiad (Class 7) Science. Open each question or exercise to read its content, reference answers and available explanation.
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Showing questions 1–30 of 65.
A heater wire carries a steady 3 A for 10 s. What total charge moves through it?Read the answer and worked solution →Which device is used to measure electric current in a circuit?Read the answer and worked solution →Conventional current is defined as the flow of which kind of charge?Read the answer and worked solution →In a metal wire, electrons move in which way compared with conventional current?Read the answer and worked solution →What carries the current through a salt solution (an electrolyte)?Read the answer and worked solution →Which of these gives direct current?Read the answer and worked solution →In alternating current, the movement of charge periodically:Read the answer and worked solution →Which device can convert alternating current into direct current?Read the answer and worked solution →A resistor of 4 ohms has 12 V across it. What current flows through it?Read the answer and worked solution →A bulb draws 0.5 A when 6 V is applied. What is its resistance?Read the answer and worked solution →The resistance of a wire stays fixed. If the voltage across it is doubled, the current:Read the answer and worked solution →A 9 V supply drives 3 A through a coil. What is the coil's resistance?Read the answer and worked solution →Two copper wires are equally thick. Which has the lower resistance?Read the answer and worked solution →Of two same-length copper wires, which offers less resistance?Read the answer and worked solution →A wire is cut to half its length. For the same material and thickness, its resistance:Read the answer and worked solution →Adding a little salt makes pure water a conductor because the salt adds:Read the answer and worked solution →Which of these materials is an electrical insulator?Read the answer and worked solution →Which of these nonmetals can conduct electricity?Read the answer and worked solution →Which metal is most commonly used in overhead power transmission lines?Read the answer and worked solution →Silver conducts slightly better than copper. Why is it rarely used for wires?Read the answer and worked solution →Which scientist first studied the heating effect of current, in 1841?Read the answer and worked solution →A bulb filament glows because current passing through it causes:Read the answer and worked solution →An electric room heater mainly uses which effect of current?Read the answer and worked solution →The watt, the unit of power, is equal to:Read the answer and worked solution →A fuse wire protects a circuit because too much current makes it:Read the answer and worked solution →In 1820 Ørsted discovered that an electric current creates:Read the answer and worked solution →Who invented the electromagnet in 1824?Read the answer and worked solution →Which US scientist improved and popularised the electromagnet from 1830?Read the answer and worked solution →Sturgeon's iron horseshoe, wrapped with wire, did what when the current stopped?Read the answer and worked solution →Electromagnets usually consist of which wire wound into a coil?Read the answer and worked solution →
Worked practice questions
Which device is used to measure electric current in a circuit?
- Voltmeter
- Barometer
- Hygrometer
- Ammeter
Show answer and solution
Correct answer: D. Ammeter
An ammeter is the instrument built to read the size of a current.
Conventional current is defined as the flow of which kind of charge?
- Positive charges
- Negative electrons
- Neutral atoms
- Photons of light
Show answer and solution
Correct answer: A. Positive charges
By convention the current direction is taken as the direction in which positive charges would flow.
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