State the equation linking charge, current and time.

Q = I × t (or I = Q ÷ t), with Q in coulombs, I in amperes and t in seconds.

A flow of 1 coulomb of charge every second.

What does potential difference measure?

The energy transferred per coulomb of charge between two points, in volts (V).

State the equation for resistance.

R = V ÷ I, which comes from V = I × R.

How is a voltmeter connected?

In parallel (across) the component.

Give one use of a variable resistor.

Changing the current, for example in a dimmer switch or volume control.

Name three control variables when investigating wire length.

Wire material, wire thickness and temperature.

Current, potential difference and resistanceIB MYP Sciences: Flashcards

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What is electric current?

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What is electric current?: The rate of flow of electric charge, measured in amperes (A).
State the equation linking charge, current and time.: Q = I × t (or I = Q ÷ t), with Q in coulombs, I in amperes and t in seconds.
What carries the charge in a metal wire?: Electrons.
What is 1 ampere?: A flow of 1 coulomb of charge every second.
What does potential difference measure?: The energy transferred per coulomb of charge between two points, in volts (V).
State the equation for resistance.: R = V ÷ I, which comes from V = I × R.
In what unit is resistance measured?: Ohms (Ω).
How is an ammeter connected?: In series with the component.
How is a voltmeter connected?: In parallel (across) the component.
What happens to the resistance of an LDR as light gets brighter?: It decreases.
What happens to the resistance of an NTC thermistor as temperature rises?: It decreases.
Give one use of a variable resistor.: Changing the current, for example in a dimmer switch or volume control.
Name three control variables when investigating wire length.: Wire material, wire thickness and temperature.
A current of 3.0 A flows for 10 s. What charge flows?: Q = I × t = 3.0 × 10 = 30 C.

Exam questions on Current, potential difference and resistance

A technician in Nairobi is testing a small solar-powered lamp. A steady current of 0.50 A flows through the lamp for 2.0 minutes.
State where an ammeter and a voltmeter should be connected to measure the current through the lamp and the potential difference across it.2 marks
A student in Seoul connects a fixed resistor to a 6.0 V battery and measures a current of 0.20 A through the resistor.
The student replaces the resistor with one of twice the resistance and keeps the same battery. Calculate the new current.2 marks
A greenhouse controller in Almería, Spain, uses a thermistor to monitor the air temperature and a light-dependent resistor (LDR) to monitor daylight. Each sensor is connected to a constant 3.0 V supply.
Describe how the resistance of the thermistor changes as the greenhouse warms up, explain the effect on the current in its circuit, and suggest how the controller could use this change.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).