Question

A dynamo is used to supply electric current to a small electric bulb, if the number of turns in the coil of this dynamo is doubled, then the voltage in the bulb
A. Will decrease
B. Remains unchanged
C. Will be doubled
D. Will increase by a factor between $1$or $2$

Answer 1

According to Faraday’s Law magnetic flux is affected by change in time, change in flux and change in turns of a coil. This magnetic flux produces voltage also. Which is directly proportional to the turns of the coil.

Complete answer:
The number of turns of a coil is directly proportional to the voltage. If the number of turns in the coil is increased, the voltage will also increase, if the number of turns in the coil is decreased, the voltage will also decrease. From Faraday’s law if N is the number of turns in a coil then the formula is- The induced voltage =$N \times \left( {d\phi /dt} \right)$.

According to this equation, it is clear that the number of turns of a coil (N) $\infty$ to the induced voltage. This will happen when the current will be direct or alternating. So here, according to this above question if the number of turns of a coil of this dynamo is doubled, the voltage in the bulb will be doubled.

The ratio of the number of two coils is equal to the ratio of two voltages. The number of turns is also directly proportional to the field lines. Increasing field lines make an electromagnet stronger, which is also directly proportional to the voltage. According to Faraday’s Law we know that the induced voltage =$N \times \left( {d\phi /dt} \right)$.

If the flux will be constant then the voltage will be directly proportional to the number of turns of the coil. Here N is equal to the number of turns.So, when a dynamo is used to supply electric current to a small electric bulb, if the number of turns in the coil of this dynamo is doubled, then the voltage in the bulb will be doubled.

Hence, option C is the correct answer.

Note: We can get confused by the magnetic flux in the equation of Faraday’s law. But this is the most important thing in this topic. This magnetic flux produces the voltage.The voltage will increase when the number of coils will also increase. This will happen only for any direct current or alternating current.