Question

A transformer steps up the voltage by a factor of 100. The ratio of current in the primary to that in the secondary is:

• A. 1
• B. 100
• C. 0.01
• D. 0.1

Hint:

Remember, for a transformer that steps up the voltage, the current in the primary coil decreases proportionally to maintain power conservation: \( V_p I_p = V_s I_s \).

Answer 1

The Correct Option is C

For an ideal transformer, the relationship between the voltage and current in the primary and secondary coils is given by: \[ \frac{V_p}{V_s} = \frac{I_s}{I_p} \] where \( V_p \) and \( I_p \) are the voltage and current in the primary coil, and \( V_s \) and \( I_s \) are the voltage and current in the secondary coil. Given that the voltage is stepped up by a factor of 100: \[ \frac{V_s}{V_p} = 100 \] Using the transformer equation: \[ \frac{V_p}{V_s} = \frac{I_s}{I_p} \quad \Rightarrow \quad \frac{I_p}{I_s} = \frac{1}{100} \] Thus, the ratio of current in the primary to that in the secondary is 0.01.