DC Motor Questions

When the electric current in wire XY is in the direction shown, there is an upward force on the wire.

If the north and south poles of the magnet exchange positions, in which direction will the force on the wire act?

• downwards

• upwards

• to the left

• to the right

Tags

NGSS.HS-PS2-5

A student carries out an experiment to see the effect of a magnetic field on a wire carrying a current. The wire moves upwards as shown.

What should the student do to make the wire move downwards?

• change the direction of the current

• move the poles of the magnet closer together

• send a smaller current through the wire

• use a stronger magnet

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

A current-carrying coil in a magnetic field experiences a turning effect.

How can the turning effect be increased?

• increase the number of turns on the coil

• reduce the size of the current

• reverse the direction of the magnetic field

• use thinner wire for the coil

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

The diagram shows a simple DC electric motor which is rotating.

Which change will make the motor rotate more quickly?

• reversing the polarity of the magnets

• reversing the battery

• removing the magnets

• using more powerful magnets

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

A simple DC electric motor is fitted with a coil that rotates in a magnetic field. A commutator connects the power supply to the coil.

What is the purpose of the commutator?

• It converts AC into DC in the coil.

• It prevents the current from becoming too great, because the coil has a low resistance

• It reverses the direction of the current in the coil after every 180° rotation of the coil

• It switches the current off momentarily after every 90° rotation of the coil

Tags

NGSS.HS-PS2-5

A coil carries a current in a magnetic field. The coil experiences a turning effect.

Which device uses this effect?

• a DC motor

• an electromagnet

• a relay

• a transformer

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

A wire XY lies between the poles of a magnet. The diagram shows the upward force on the wire XY caused when there is an electric current in the direction XY as shown.

Three tests are made using this apparatus:

1 The current direction is reversed.

2 The N and S poles are swapped around.

3 The current is switched off.

Which will result in no change in the size of the force on the wire?

• 1 and 2 only

• 1 only

• 2 only

• 3 only

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

The diagram shows a current-carrying wire placed between two magnetic poles. The current is in the direction shown.

What is the direction of the force on the wire?

• towards the bottom of the page

• towards the top of the page

• towards the left-hand side of the page

• towards the right-hand side of the page

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

A current-carrying wire lies between the poles of two magnets, as shown.

What is the direction of the force on the wire?

• into the plane of the paper

• out of the plane of the paper

• towards the left

• towards the right

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

What does not alter the size of the turning effect on the coil of an electric motor?

• the strength of the magnetic field

• the direction of the current in the coil

• the number of turns in the coil

• the size of the current in the coil

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5