ELECTROMAGNETIC INDUCTION

Which statement describes electomagnetic induction ?

• the production of an e.m.f across an electrical conductor when there is relative movement between the conductor and a magnetic field

• the production of an e.m.f across an electrical conductor when there is no movement between the conductor and a magnetic field

• the production of an e.m.f across an electrical conductor when there is relative movement between the conductor and an induced current

• the production of an e.m.f across an electrical conductor when there is no movement between the conductor and an induced current

Which of the following would not induce a current :

• Moving a wire between the poles of a magnet

• Taking a bar magnet out of a coil or wire

• Holding a wire between the poles of a magnet

• Spinning a coil or wire in a magnetic field

The principle of electromagnetic induction is discovered by .....

• Hans Christian Oersted

• Heinrich Friedrich Emil Lenz

• Michael Faraday

• Hendrik Antoon Lorentz

An e.m.f is induced across a wire when it moves through the magnetic field between the poles of a magnet. which electrical device operates because of this effect ?

• a battery

• a cathode-ray tube

• a generator

• a motor

A student investigates the effect of moving a bar magnet into a coil.  She measures the current which flows in the coil when she moves the magnet. Which change would increase the current ?

• 1. Using a stronger bar magnet

• Moving the magnet in the opposite direction

• Moving the coil instead of the magnet

• Moving the coil from side to side as well as in and out of the magnet

Which statement is true ?

• A step-down transformer decreases current

• A step-up transformer increases voltage

• A step-up transformer is used in a school laboratory power supply

• A step-down transformer has more turns on the secondary coil than on the primary coil

Which one of these is not needed for electromagnetic induction  ?

• A conductor

• Movement

• A coil of wire

• 1. A magnetic field

lenz's law says ....

• the direction of an induced voltage

  always opposes the change in the circuit or the

  magnetic field that produces it

• the direction of an induced current

  always opposes the change in the circuit or the

  magnetic field that produces it

• the direction of magnetic flux

  always opposes the induced current in the circuit

• the direction of an induced current

  always similar to the change in the circuit or the

  magnetic field that produces it

The diagram shows a coil and a magnet. When the magnet is moved away from the coil, current flows

Which one of the following describes what happens ?

• Current flows clockwise in the coil, creating a north pole which attracts the sout pole of the bar magnet

• Current flows anticlockwise, creating a north pole which repels the south pole of the bar magnet

• Current flows anticlockwise, creating a south pole which repels the south pole of the bar magnet

• Current flows anticlockwise, creating a north pole which attracts the south pole of the bar magnet

The size of the e.m.f induced in a coil can be increased by increasing below, EXCEPT .....

• the turns of wire

• strength of the magnetic field

• speed of the relative movement

• distance from power station