In a transformer, if the primary voltage is 120V and the secondary voltage is 12V with a load current of 20 amps, what will be the primary current?

To determine the primary current in a transformer given the primary and secondary voltages and the load current, you can use the principle of conservation of power, which states that the power on the primary side equals the power on the secondary side.

In a transformer, the relationship between primary and secondary voltages and currents can be described by the formula:

[

P_{primary} = P_{secondary}

]

Where:

[

P = V \times I

]

From the question, the primary voltage (V1) is 120V, the secondary voltage (V2) is 12V, and the load current in the secondary (I2) is 20 amps.

First, calculate the power on the secondary side:

[

P_{secondary} = V2 \times I2 = 12V \times 20A = 240W

]

Since power in the transformer is conserved (ignoring losses), the primary power also equals 240W. The primary current (I1) can then be calculated using the primary voltage:

[

P_{primary} = V1 \times I1

]

Setting the primary power equal to the secondary power gives:

[

240W = 120