Magnetic Fields in Wires Flashcards

All 6 cards in this deck

What are the steps to show that a current in a wire creates a magnetic field?
e.g. using a power pack, a wire, a card and iron filings

1. Put the wire through a hole in the card and connect the wire to a power pack.
2. Sprinkle iron filings on the card and switch on, so there is a current in the wire.
3. Tap the card — the filings move into circles around the wire.

What shape are the magnetic field lines around a long straight current-carrying wire?

Circles around the wire.
An arrow on a field line (e.g. clockwise) shows the direction of the field.

True or false? Reversing the direction of the current in a wire reverses the direction of its magnetic field.

True.
The circular field lines stay the same shape but the arrows point the other way round.

What is the relationship between the magnetic field strength around a wire and the size of the current?

Directly proportional.
As the current increases, the field strength increases in even steps.

True or false? The magnetic field around a current-carrying wire is strongest close to the wire.

True.
The field gets weaker further from the wire, so the field lines are closer together near it.

How do you use the right-hand thumb rule to find the direction of the magnetic field around a current-carrying wire?

Grip the wire with your right hand so your thumb points along the current. Your curled fingers show which way the field circles the wire.