# Magnetic Fields

12PHYS - Electricity

2019

# Mahi Tuatahi

The battery is 12V.

1. When switched on, how many joules of energy does the cell supply to each coulomb of charge that flows out of the cell? (A)

1. When the cell is switched on, the resistance of the lamp is $$9\Omega$$. Calculate the current flowing through the lamp. (A)
2. State the meaning of the term resistance in terms of electron flow. (A)

# Magnetic Fields

Magnetic fields can be found in two places:

• Around magnetic objects
• Around current carrying wires

## Right Hand Grip Rule 1

• Used to find the direction of the current or magnetic field when you know the other.
• This version of the right hand grip rule only applies to current carrying wires!

## Right Hand Grip Rule 2

• Used to find the direction of the magnetic field in a coil of wire.

## Magnetic Elements

### Ferromagnetism

• Includes Co, Fe and Ni
• Permanent magnets
• Were exposed to a strong external magnetic field and retained the field after being removed from it

### Paramagnetism

• Includes Na, Mg, Ca etc.
• Can form a weak internal magnetic field when exposed to an external magnetic field
• Feel a small attractive force

### Diamagnetism

• Includes Cu, Si, N, C etc.
• Can form a weak internal magnetic field when exposed to an external magnetic field
• Feel a small repulsive force