Question
Three cores of different metals P, Q and R are placed inside identical coils of wire.
At least one of the metals is non-magnetic. The cores are held above some iron nails.
The three diagrams show what happens when there is a current in the coils.
The three diagrams below show what happens when the current is then switched off.
Which core metals are magnetic?
A P only
B R only
C P and Q
D Q and R
Answer/Explanation
Ans: D
Question
The diagram shows an electromagnet near a coil of wire connected to a voltmeter. The reading on the voltmeter is zero.
The switch is closed. The electromagnet magnetises quickly. What happens to the reading on the voltmeter?
It keeps increasing.
It quickly increases and stays at maximum.
It quickly increases and then decreases.
It stays on zero.
Answer/Explanation
Ans: C
Question
A solenoid is connected to a very sensitive ammeter. A rod is inserted into one end of the solenoid. The ammeter shows that there is a small electric current in the solenoid while the rod is moving.
Which rod is being inserted?
a heated copper rod
a magnetised steel rod
an uncharged nylon rod
a radioactive uranium rod
Answer/Explanation
Ans: B
Question
Four small compasses are placed around a solenoid.
A current is now switched on in the solenoid.
Which diagram shows possible new directions of the compass needles?
Answer/Explanation
Ans: D