Chapter 25.2, Problem 21SSC

To determine

To Explain: The reason why transformers made with few turns of coil are made up of thick wires and transformers with more turns of coil are made up of thin wires.

Answer to Problem 21SSC

Large amount of current can pass through the coil that has less turns. So, the thick wires having the capacity for more amount of current that are required for the transformers.

Explanation of Solution

Introduction:

The device used to decrease or increase AC voltages is called a transformer. This device is widely used because it changes voltages with relatively less loss of energy. It is used for transferring electrical energy from one circuit to another circuit by electromagnetic induction.

Transformer contains of two coils which are electrically isolated and also operates on faraday’s principle of mutual induction.

The two coils are electrically insulated but are wound around a single iron core. The name of first coil is primary coil and second coil is secondary coil.

In transformer, when the primary coil is linked or connected to a source of alternating current voltage, the changing current produces a varying magnetic field. The varying magnetic field is carried via iron core to another coil (or the secondary coil).

In the secondary coil, varying field induces a varying electromagnetic field (or EMF). This effect is termed as a mutual inductance. The EMF induced in the secondary coil is called the secondary voltage. This secondary voltage is proportional to the primary voltage.

Because of this more current will go through the coil with fewer turns. So, thick wires with capacity for greater currents are required. Also, resistance must be kept low to prevent voltage drops and $r^{2}R$ power loss and heating.

Conclusion:

Large amount of current can pass through the coil which has less turns. So, thick wires with capacity for greater currents are required for transformers. The resistance of the transformers must be kept low in order to avoid the drop of voltage and loss of power and the heating.