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Current & Resistance

1. An ant is 3 cm from a magniflying lens with a focal length of 5 cm. The image of the bug is
A. real, upright, enlarged, other side of lens
B. virtual, upright, enlarged, same side of lens
C. virtual, smaller, inverted, same side of lens
D. real, upright smaller, other side of lens

A 5kW heater is connected to a 200 V source of emf

2. What is the current through the heater?

3. What is the resistance of the heater?

4. If the voltage remained the same and the resistance tripled what would happen to the power dissipation?
A. it would increase
B. it would decrease
C. there would be no change

Solution Preview

1. u = 3 cm, f = 5 cm
i/u -1/v = 1/f ----> v = 7.5 cm
Now height of image / height of object = v/u = 7.5/3 = 2.5
Image ...

Solution Summary

The solution gives short, clear answers to the questions on the orientation of the image of an ant viewed through a magnifying lens as well as the questions on current, resistance and power dissipation in a 5kW heater.

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