Physics · Electricity. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Current is the rate of flow of electrical charge. Potential difference (p.d.) pushes the charge round the circuit. Resistance opposes the current. For a given p.d., a bigger resistance gives a smaller current.
For a fixed resistor at constant temperature, the current is directly proportional to the p.d., so its I–V graph is a straight line through the origin. Other components do not behave like this. A filament lamp gives a curve, because its resistance rises as it gets hotter. A diode lets current pass in one direction only.
An ammeter goes in series with the component. A voltmeter goes in parallel across it.
Students use time in minutes in Q = It. Always change the time into seconds first (2 minutes = 120 s).
Answer: Resistance = 20 Ω and charge = 6.0 C
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