Generators, EMF, and Oscilloscope

The graph shows the output of an a.c. generator. The coil in the generator rotates 20 times in one second.

Which graph shows the output when the coil rotates 10 times in one second?

• 
• 
• 
• 

A magnet is suspended from a spring so that it can move freely inside a coil. The coil is connected to a sensitive centre-zero ammeter.

What does the ammeter show when the magnet repeatedly moves slowly up and down?

• a reading constantly changing from left to right and right to left

• a steady reading to the left

• a steady reading to the right

• a steady reading of zero

A coil is rotated steadily between the poles of a magnet. The coil is connected to an oscilloscope.

Which graph shows the output voltage V against time t?

• 
• 
• 
• 

A wire passes between the poles of a horseshoe magnet. There is a current in the wire in the direction shown, and this causes a force to act on the wire.

Which arrangement or arrangements will cause a force in the same direction as the original arrangement?

• P, Q and R

• P and Q only

• P only

• R only

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

The diagram shows a flat, rectangular coil placed between the poles of a magnet.

There is a current in the coil that makes it turn in the direction shown in the diagram.

Which change would make the coil turn in the opposite direction?

• decreasing the current in the coil

• increasing the number of turns on the coil

• reversing both the direction of the current in the coil and the poles of the magnet

• reversing only the direction of the current in the coil

Which diagram represents the voltage output of a simple a.c. generator?

• 
• 
• 
• 

The diagram shows a coil of wire connected to a voltmeter.

A student has a magnet and an unmagnetised iron rod.

How can an e.m.f. be induced across the coil?

• holding the magnet inside the coil

• holding the iron rod inside the coil

• pushing the magnet into the coil

• pushing the iron rod into the coil

The diagram shows an experiment to demonstrate electromagnetic induction.

X and Y are joined, in turn, by four wires, each made of a different material.

Each wire is then moved quickly downwards between the magnets.

Which material will not give rise to an induced current in the wire?

• aluminium

• copper

• iron

• nylon

Which diagram shows a movement that will not produce the changing magnetic field needed to induce an e.m.f. in the coil?

• 
• 
• 
•