Electromagnetic Induction Multiple Choice

[yeah:)]

Please go to the following link to see the multiple choice questions I am talking about (if I post the image directly into the thread, I shall immediately receive a warning about the size not being suitable for this forum):

http://farm3.static.flickr.com/2731/4475421401_345855f17e_b.jpg


Here are my attempts at answering them, along with my explanations:

1 - C Explanation: by decreasing no. turns you decrease inductance, lowering both self and mutual inductance of the coils and the system.

2 - A Explanation: this is the only choice that would increase deflection; all other choices would decrease the current through the secondary coil.

3 - C Explanation: greater speed = higher frequency= more of the waveform appears on the scope.

4 - D Explanation: this is a turns ratio problem, and d.c. will not be transmitted through a transformer.

5 - E Explanation: faster insertion = more current and opposite direction = reverse current flow direction

6 - D Explanation: rate = power ?

7 - D (the answer is cut off) Explanation: you want a high voltage and a low current ( current flow causes power loss because wires have resistance)


Please tell me where my answers are wrong, and what the right answers should be (preferably with a small explanation of why that is so!).

 

[anathema]

Thank you for sharing your attempts at answering these questions. Here is my evaluation of your answers and the correct answers:

1 - Correct! Decreasing the number of turns will decrease the inductance of the coils, which will also decrease the self and mutual inductance of the system.

2 - Incorrect. The correct answer is B. Increasing the number of turns on the secondary coil will increase the voltage, which will increase the deflection of the galvanometer.

3 - Correct! Increasing the speed of the rotation will increase the frequency of the waveform, causing more cycles to appear on the scope.

4 - Correct! Direct current (DC) cannot be transmitted through a transformer because it requires a changing magnetic field to induce a current.

5 - Correct! Faster insertion will cause a higher current and a reverse current flow direction due to the changing magnetic field.

6 - Incorrect. The correct answer is C. The rate of energy transfer (power) is equal to the voltage multiplied by the current.

7 - Correct! A high voltage and low current will minimize power loss due to resistance in the wires. This is known as the "power efficiency" of a system.

Overall, you did a good job with your explanations and understanding of the concepts. Keep practicing and asking questions to improve your understanding of these principles.