Electromagnetic Induction: Answers

How can voltage be induced in a coil of wire?

Voltage can be induced in a wire by placing it in proximity to a magnetic field. This could be done in 2 ways: moving a bar magnet inside a coil of wire or by moving the coil of wire in a magnetic field.

How can the size of the induced voltage be increased?

The size of the induced voltage can be increased by increasing the strength of the magnet, increasing the number of turns on the coil or by moving the magnet into the coil of wire faster.

Describe how transformers are used to minimise energy loss when transmitting electricity to homes.

Transformers can minimise energy loss by increasing the voltage (this is done by a step-up transformer). A higher voltage means the electricity now has a lower current. The lower the current, the less energy is wasted as it travels through power cables to homes. A step-down transformer would then be used to decrease the voltage (which would increase the current).

A step-up transformer is used to increase the voltage of 10 V of current. There are 5 turns on the primary coil and 20 turns on the secondary coil. What is the output voltage?

Use the equation: primary voltage x secondary voltage = number of turns on primary coil x number of turns on secondary coil.

• Vp / Vs = Np / Ns

• 10 x ? = 5 x 20

• 10 x ? = 100

• Secondary (output) voltage = 10

A step-down transformer decreases the electricity voltage from 100 V to 30 V. If the initial current is 3 A, what is the final current?

Use the equation: primary voltage x primary current = secondary voltage x secondary current

• VpIp = VsIs

• 100 x 3 = 30 x ?

• 300 = 30 x ?

• Final current = 10 A