State the equation linking charge, current and time.

Q = I × t (charge in C, current in A, time in s).

The charge that passes a point in one second when the current is one ampere.

In which direction does conventional current flow?

From the positive terminal to the negative terminal.

In which direction do electrons flow in a circuit?

From the negative terminal to the positive terminal.

What is potential difference?

The energy transferred per unit charge between two points.

What does a potential difference of 1 V mean?

One joule of energy is transferred for each coulomb of charge.

What is the difference between a cell and a battery?

A cell is a single unit; a battery is two or more cells connected together.

How is an ammeter connected?

In series with the component, in the same loop.

How is a voltmeter connected?

In parallel, across the component.

What would happen if an ammeter was connected in parallel?

It would act as a short circuit, allowing a very large current.

Current and potential differenceIB MYP Physics: Flashcards

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What is electric current?

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What is electric current?: The rate of flow of electric charge.
State the equation linking charge, current and time.: Q = I × t (charge in C, current in A, time in s).
What is one coulomb?: The charge that passes a point in one second when the current is one ampere.
What carries the current in a metal wire?: Free electrons.
In which direction does conventional current flow?: From the positive terminal to the negative terminal.
In which direction do electrons flow in a circuit?: From the negative terminal to the positive terminal.
What is potential difference?: The energy transferred per unit charge between two points.
State the equation linking energy, charge and potential difference.: E = Q × V (V = E ÷ Q).
What does a potential difference of 1 V mean?: One joule of energy is transferred for each coulomb of charge.
What is the difference between a cell and a battery?: A cell is a single unit; a battery is two or more cells connected together.
How is an ammeter connected?: In series with the component, in the same loop.
How is a voltmeter connected?: In parallel, across the component.
What would happen if an ammeter was connected in parallel?: It would act as a short circuit, allowing a very large current.
What must you do to a time given in minutes before using Q = I × t?: Convert it to seconds.

Exam questions on Current and potential difference

A camping torch has a small lamp that is powered by a 6.0 V battery. A family on a night walk in the Hajar Mountains switches the torch on and leaves it running for a short time.
Calculate the energy transferred to the lamp when 60 C of charge passes through it from the 6.0 V battery.2 marks
A student builds a simple circuit from a cell, a switch and a lamp, joined together with copper wires. She wants to find out how charge moves in the wires and to measure the current through the lamp and the potential difference across it.
State the direction of conventional current in the circuit and explain why this is opposite to the direction in which the electrons move.2 marks
A student investigates how the current through a small filament lamp depends on the potential difference across it. She connects the lamp to a variable power supply, with an ammeter and a voltmeter, and measures the current for four different values of potential difference.
State a testable hypothesis for this investigation, give a scientific reason for it, and identify the dependent variable.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).