Magnetic Fields in Wires Flashcards
All 7 cards in this deck
What is the shape of the magnetic field around a long straight current-carrying wire?
Concentric circles centred on the wire, in planes at right angles to it.
What apparatus is used to show that a current in a long straight wire produces a magnetic field?
A vertical wire pushed through a horizontal card, with plotting compasses (or iron filings) on the card; when the current is switched on they show circular field lines.
What are the steps to find the direction of the magnetic field around a straight current-carrying wire?
e.g. conventional current flowing vertically upwards
- Grip the wire with your right hand, thumb pointing along the conventional current: thumb points up.
- Your curled fingers give the field direction: field circles the wire.
- Viewed from above, the field goes anticlockwise.
What two things determine the strength of the magnetic field around a long straight wire?
The size of the current (bigger current, stronger field) and the distance from the wire (further away, weaker field).
Which way does a plotting compass needle point when placed on a card around a current-carrying wire?
Along the field line at that point, i.e. tangential to the circular field lines.
True or false? The magnetic field lines around a straight current-carrying wire run parallel to the wire.
False. They are concentric circles around the wire, at right angles to it.
True or false? The magnetic field around a long straight current-carrying wire gets weaker the further you move away from the wire.
True. Field strength decreases with distance from the wire (and increases with larger current).