CBSE Class 12 Physics Previous Year Question Paper 2012
This is the CBSE Class 12 Physics Previous Year Question Paper from 2012, focusing on AC Devices. The paper includes questions carrying 1 and 2 marks, testing fundamental concepts of transformers. Students are asked to identify properties of transformer core materials, explain the function of step-up transformers, and list factors responsible for energy losses. It also delves into the principle of transformers, their application in large-scale power transmission, and why they cannot be used for DC voltage. The paper covers energy losses like eddy currents, flux leakage, and copper loss. Solving this previous year's paper provides valuable insights into the exam pattern and helps students strengthen their understanding of AC circuits and devices for effective exam preparation.
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Quick info
| Board | CBSE |
|---|---|
| Class | 12 |
| Subject | Physics |
| Session | 2012 |
| Language | English |
| Type | Previous Year Question Paper |
| Exam type | Board Exam |
Paper pattern
The paper contains 1-mark and 2-marks questions, covering topics related to AC Devices and transformers.
Topics covered
Paper topics
- Transformers
- AC Devices
- Mutual Induction
- Energy Losses in Transformers
- Step-up Transformer
- Eddy Currents
- Flux Leakage
- Copper Loss
Important topics
- Principle of Transformer
- Energy Losses in Transformers
- Application of Transformers in Power Transmission
PDF preview
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Question paper text
AC Devices
1 Mark Questions
- Mention the two characteristic properties of the material suitable for making core of a transformer. [All India 2012]
Ans. (i) Low retentivity or coercivity.
- Low hysterisis loss or high permeability and susceptibility.
- What is the function of a step-up transformer? [All India 2011C]
Ans. Step-up transformer converts low alternating voltage into high alternating voltage and high alternating current into low alternating current. The secondary coil of step-up transformer has a greater number of turns that the primary <math>(N_s > N_P)</math>
- Write any two factors responsible for energy losses in actual transformers. [Delhi 2009c]
Ans. Two factors for energy losses are
- eddy currents
- hysterisis loss
2 Marks Questions
- State the underlying principle of a transformer. How is the large scale transmission of
electric energy over long distances done with the use of transformers? [All India 2012]
Ans. Principle of transformer A transformer is based on the principle of mutual induction, i.e. whenever the amount of magnetic flux linked with a coil changes, an emf is induced in the neighbouring coil.
Power transmission Electric power is transmitted over long distances at high voltage. So, step- up transformers are used at power stations to increase the voltage of power whereas a series of step-down transformers are used to decrease the voltage up to 220 V.
- State the principle of working of a transformer. Can a transformer be used to step-up or
step-down a DC voltage? Justify your answer. [All India 2011]
Ans. (i) For principle of transformer A transformer is based on the principle of mutual induction, i.e. whenever the amount of magnetic flux linked with a coil changes, an emf is induced in the neighbouring coil.
- No, transformer cannot be used to change DC voltage. This happens because DC voltage cannot change flux linked with primary or secondary coils.
- Mention various energy losses in a transformer. [All India 2011]
Ans. Energy losses in transformer:
- Eddy current loss Eddy current in iron core of transformer facilitates the loss of energy in the form of heat.
- Flux leakage Total fluxes linked with primary do not completely pass through the secondary which denotes the loss in the flux.
- Copper loss Due to heating, energy loss takes place in copper wires of primary and secondary Coils.
Frequently asked questions
What is this document?
This is a CBSE Class 12 Physics Previous Year Question Paper from 2012, focusing on AC Devices.
What topics are covered in this paper?
The paper covers topics such as the principle of transformers, their applications, energy losses (eddy currents, flux leakage, copper loss), and the properties of transformer core materials.
How can solving this previous year paper help?
Solving this previous year question paper helps students understand the exam pattern, identify important concepts, and improve their problem-solving skills for the CBSE Class 12 Physics board exam.
Can a transformer be used for DC voltage?
No, a transformer cannot be used to step-up or step-down DC voltage because DC voltage does not cause a change in magnetic flux linked with the coils, which is essential for transformer operation.
What are the main energy losses in a transformer?
The main energy losses in a transformer are eddy current loss, flux leakage, and copper loss.
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