Advertisements
Advertisements
Question
How are the e.m.f in the primary and secondary coils of a transformer related with the number of turns in these coils?
Advertisements
Solution
`"E"_"s"/"E"_"p" = "N"_"s"/"N"_"p"` = turns ratio n
where, s stands for secondary and p stands for primary.
i.e. `"E.M.f. in secondary coil"/"E.m.f. in primary coil" = "Number of turns in primary coil"/"Number of turns in secondary coil"`
APPEARS IN
RELATED QUESTIONS
The teachers of Geeta’s school took the students on a study trip to a power generating station, located nearly 200 km away from the city. The teacher explained that electrical energy is transmitted over such a long distance to their city, in the form of alternating current (ac) raised to a high voltage. At the receiving end in the city, the voltage is reduced to operate the devices. As a result, the power loss is reduced. Geeta listened to the teacher and asked questions about how the ac is converted to a higher or lower voltage.
1) Name the device used to change the alternating voltage to a higher or lower value. State one cause for power dissipation in this device.
2) Explain with an example, how power loss is reduced if the energy is transmitted over long distances as an alternating current rather than a direct current.
3) Write two values each shown by the teachers and Geeta.
The adjacent diagram shows a coil would around a soft iron bar XY. (a) State the polarity at the end X and Y as the switch is pressed. (b) Suggest one way increasing the strength of electromagnet so formed.
State the principle of a step-up transformer. Explain, with the help of a labeled diagram, its working ?
Describe briefly and two energy losses, giving the reasons for their occurrence in actual transformers ?
Describe briefly, with the help of labelled diagram, working of a step-up transformer.
A step-up transformer converts a low voltage into high voltage. Does it not violate the principle of conservation of energy? Explain.
Explain step up and step down transformer?
Give the advantage of AC in long distance power transmission with an illustration.
A step-down transformer connected to the main supply of 220 V is used to operate 11V,88W lamp. Calculate
- Voltage transformation ratio and
- Current in the primary
For what purpose are the transformers used?
