Electromagnetism is due to the magnetic fields around electric currents. The fields can cause forces with other nearby magnets and these forces can be used to make motors spin.
What will increase the strength of the magnetic field around a wire carrying a current?
Increasing the current
Moving further from the wire
Switching the current off
What is the effect of putting an iron core inside a solenoid?
The magnetic field gets weaker
The iron core cancels the magnetic field
The electromagnet becomes stronger
An electric current flows through a wire. What happens to the magnetic field strength when the wire is shaped into a solenoid?
It stays the same
What do a bar magnet and a solenoid have in common?
They are both permanent magnets
Their magnetic fields have a similar shape
They are both types of electromagnet
Which of the following does NOT increase the strength of the magnetic field produced by an electromagnet?
Increasing the electric current flowing in the coil
Increasing the number of turns on the coil
Using a copper core
What is the direction of the force produced on a wire carrying a current when placed in a magnetic field?
At right angles to the magnetic field and the wire
Parallel to the magnetic field but right angles to the wire
Parallel to the wire but at right angles to the magnetic field
When using Fleming's left-hand rule, what does the thumb direction represent? - Higher
0.4 A flows in 0.1 m of wire in a 0.7 T magnetic field. What force acts on the wire? - Higher
In a dc motor, what is the function of the split ring commutator? - Higher
It reverses the current direction every half turn, to keep the motor spinning in the same direction all the time
It shields the magnetic field from acting outside the motor case
It strengthens the magnetic field to make the motor spin fast on a lower current
A wire wrapped around an iron ‘C’ core makes an electromagnet. What effect will increasing the number of turns of wire have on it?
A stronger magnetic field but no increase in the number of paper clips picked up
A stronger magnetic field and an increase in the number of paper clips picked up
No effect on the strength of the magnetic field and no increase in the number of paper clips picked up