Malaysia SPM Form 5 Physics - Electromagnetism

1.1 Introduction to Magnetism
1.2Straight Wire and Coil
1.3 Solenoid
1.4 Uses of Electromagnet
2.1 Catapult Force
2.2 Application of Catapult Force
3.1 Electromagnetic Induction
3.2 DC and AC Generator
4.1 Transformer
4.2 Transformer - Calculation
5.1 Generation and Transmission of electricity

Transformer - Calculation Question

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1. A transformer has primary coil with 2500 turns and secondary coil with 1500 turns is connected to a 240V power supply. Find the voltage of the secondary coil.
Choice 1 400V
Choice 2 144V
Choice 3 200V
Choice 4 120V

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2. An ideal transformer is supplied with voltage 240V. It is found that the potential difference of the secondary coil is 12V and the current is 3A. Find the current in the primary coil.
Choice 1 6.67A
Choice 2 0.15A
Choice 3 0.25A
Choice 4 0.0125A

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3. An alternating current of 2A is supplied to a transformer. Given that the efficiency of the transformer is 75%. If the potential difference and current of the output is 1200V and 0.3A respectively. Find the potential difference across the primary coil.
Choice 1 120V
Choice 2 360V
Choice 3 900V
Choice 4 240V

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4. A step down transformner is used to lower the voltage of a supply from 240V to 60V. The current flow in primary coil and secondary coil are 2A and 6A respectively. Determine the efficiency of the transformer.
Choice 1 25%
Choice 2 50%
Choice 3 75%
Choice 4 90%

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5. The primary coil of a transformer is connected to a 240V a.c. supply and an output voltage of 6V is detected in the secondary coil. Find the ratio of the number of windings in the secondary coil to the number of windings in the promary coil.
Choice 1 1 : 40
Choice 2 40 : 1
Choice 3 1 : 20
Choice 4 20 : 1

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electromagnetism notes