Question

Name the type of transformer shown in Fig. What changes will you observe regarding the brightness of the lamp, if

1. the number of turns in the secondary is doubled? Explain.
2. the part X of the transformer is removed?
3. the core of the transformer is made out of copper?
4. the A.C. supply is replaced by D.C.?

Answer 1

Step-down transformer, because the primary coil has more turns than the secondary coil.

1. The bulb glows brighter because doubling the number of turns in the secondary coil increases the induced e.m.f. and output voltage.
2. The bulb becomes dimmer because removing part X creates an open magnetic core, increasing magnetic flux leakage and reducing the induced e.m.f.
3. The bulb becomes very dim because a copper core produces large eddy currents, causing energy loss, and does not provide an effective magnetic path.
4. The bulb does not glow continuously because DC produces a constant magnetic field after switching on, so no e.m.f. is induced in the secondary coil.