Question 399: AC fundamentals

Question

A step up transformer operates on $$220 \mathrm{~V}$$ and supplies current of $$2 \mathrm{~A}$$. The ratio of primary and secondary windings is $$1: 20$$. The current in the primary is

Accepted Answer

To determine the current in the primary winding, we can use the principle of conservation of energy, which states that the power input to the transformer should be equal to the power output (ignoring losses for simplicity).
The primary voltage is given as $$220 \mathrm{~V}$$, and the current in the secondary is given as $$2 \mathrm{~A}$$. The ratio of the primary winding to the secondary winding is given as $$1:20$$.
The formula for the ratio of the voltage in a transformer is:
$$ \frac{V_p}{V_s} = \frac{N_p}{N_s} $$
Given the winding ratio $$\frac{N_p}{N_s} = \frac{1}{20}$$, we can calculate the voltage in the secondary winding:
$$ \frac{V_p}{V_s} = \frac{1}{20} \implies V_s = 220 \mathrm{~V} 	imes 20 = 4400 \mathrm{~V} $$
Now, using the power equation for the transformer:
$$ P_{	ext{primary}} = P_{	ext{secondary}} $$
Since power $$P$$ is given by $$P = VI$$ (where $$V$$ is voltage and $$I$$ is current), we can write:
$$ V_p 	imes I_p = V_s 	imes I_s $$
Substituting the given values:
$$ 220 \mathrm{~V} 	imes I_p = 4400 \mathrm{~V} 	imes 2 \mathrm{~A} $$
Solving for $$I_p$$:
$$ I_p = \frac{4400 \mathrm{~V} 	imes 2 \mathrm{~A}}{220 \mathrm{~V}} = 40 \mathrm{~A} $$
Thus, the current in the primary winding is $$40 \mathrm{~A}$$. Therefore, the correct option is:
Option C

Answer

5 A

Answer

2 A

Answer

40 A

Answer

20 A

AC fundamentals

A step up transformer operates on $220 \mathrm{~V} and supplies current of 2 \mathrm{~A}. The ratio of primary and secondary windings is 1: 20$. The current in the primary is

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