has evenly spaced field lines and the strength of the magnetic field is the same everywhere

indicates the direction a conducting wire is forced to move in a uniform magnetic field

is a measure of the strength of a magnetic field

is the unit that magnetic flux density is measured in

The motor effect

Physics

In the Magnets and electromagnets unit, pupils learnt about rules for magnets, magnetic fields of bar magnets, and the properties and uses of electromagnets. 

Electromagnetism

It is always greater if the magnet is larger.

It is always greater if the magnetic field is stronger.

Which of the following statements about magnetic flux density are correct?

They are circular, with their centres on the wire.

They have the same shape as the field lines around a bar magnet.

They are straight and point in the same direction as the current.

They are straight and point in the opposite direction to the current.

Which of the following describes the magnetic field lines near a straight current-carrying wire?

Its field lines are perpendicular to each other.

The arrows on its field lines all point in the same direction.

Which of the following are characteristics of a uniform magnetic field?

represents the direction of the current in the wire

is not used in Fleming’s left-hand rule

represents the direction of the force on the wire

Fleming’s left-hand rule can be used to predict the direction of the force on a current-carrying wire in a magnetic field. Match each digit with what it represents in the left-hand rule.

A 12 cm length of straight wire carrying a current of 1.2 A is in a uniform magnetic field with flux density 0.50 T. The size of the force on the wire is {{}} N.

The diagram shows a current-carrying loop of wire in a uniform magnetic field. Three sides of the loop are labelled P, Q and R. Match each side to a description of the force acting on it.

The closeness of the field lines does not mean anything.

The magnetic field is stronger where the field lines are closer together.

The magnetic field is weaker where the field lines are closer together.

In a drawing of the magnetic field lines around a magnet, the field lines are closer together in some areas than others. Which of the following statements is correct?

The directions of the forces on a north-facing pole.

The directions of the forces on a south-facing pole.

What do the directions of magnetic field lines represent?

It is near a wire that is carrying a current.

It is near the north-seeking end of a bar magnet.

It is near the south-seeking end of a bar magnet.

A compass usually points north. If the needle of a compass is deflected (changes direction) so that it no longer points north, which of the following are possible explanations?

Magnetic field line arrows point towards a north-seeking pole.

Magnetic field line arrows point towards a south-seeking pole.

Current flows from the positive terminal to the negative terminal of a battery.

Current flows from the negative terminal to the positive terminal of a battery.

Which of the following statements are correct?

Two variables have this relationship: whenever the value of one variable is multiplied by a number, the value of the other variable is multiplied by the same number. The two variables are directly...

Two equal and opposite forces act on the ends of a ruler as shown by the arrows. The ruler is initially stationary. Which of the following describes what happens to the ruler?

This lesson will soon be taken down.

The motor effect

Lesson outcome