Question

the transformer is working on a 240V AC and supplies a voltage of 12V to an electric bell to the output circuit . Calulate the number of turns in the secondary coil if the number of turns in the first coil is 5000​

Answer 1

Given :

Input voltage = 240V

Output voltage = 12V

No. of turns in primary coil = 5000

To Find :

No. of turns in the secondary coil.

Solution :

❖ The voltage and currents in a transformer are related as

$\dag\:\underline{\boxed{\bf{\purple{\dfrac{V_s}{V_p}=\dfrac{I_p}{I_s}=\dfrac{N_s}{N_p}=k}}}}$

• For step-up transformer, k > 1 and for step-down transformer k < 1

By substituting the given values;

$\sf:\implies\:\dfrac{V_s}{V_p}=\dfrac{N_s}{N_p}$

$\sf:\implies\:\dfrac{12}{240}=\dfrac{N_s}{5000}$

$\sf:\implies\:N_s=5000\times\dfrac{1}{20}$

$:\implies\:\underline{\boxed{\bf{\gray{N_s=250\:Turns}}}}$

Knowledge BoosteR :

• The small transformers are self-cooled, which transfer heat directly to the surrounding. Large transformers are cooled by placing them in oil tanks to prevent overheating.
• A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages/currents. It does not affect the frequency of a.c.

Answer 2

Given :

Input voltage = 240V

Output voltage = 12V

No. of turns in primary coil = 5000

To Find :

No. of turns in the secondary coil.

Solution :

❖ The voltage and currents in a transformer are related as

$\dag\:\underline{\boxed{\bf{\purple{\dfrac{V_s}{V_p}=\dfrac{I_p}{I_s}=\dfrac{N_s}{N_p}=k}}}}$

For step-up transformer, k > 1 and for step-down transformer k < 1

By substituting the given values;

$\sf:\implies\:\dfrac{V_s}{V_p}=\dfrac{N_s}{N_p}$

$\sf:\implies\:\dfrac{12}{240}=\dfrac{N_s}{5000}$

$\sf:\implies\:N_s=5000\times\dfrac{1}{20}$

$:\implies\:\underline{\boxed{\bf{\gray{N_s=250\:Turns}}}}$

Knowledge BoosteR :

The small transformers are self-cooled, which transfer heat directly to the surrounding. Large transformers are cooled by placing them in oil tanks to prevent overheating.

A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages/currents. It does not affect the frequency of a.c.