Moving Charges And Magnetism

Correct answer: dynamo

Explanation:
The development of electromagnetism led to the invention of the dynamo, a device that converts mechanical energy into electrical energy using the principle of electromagnetic induction.

Michael Faraday discovered electromagnetic induction, which is the basic working principle behind dynamos and electric generators.

Other options:
- Electric bulb: works on the principle of heating effect of electric current.
- Electric geyser: uses the heating effect of current, not directly related to electromagnetism.
- Battery: produces electricity through chemical reactions, not based on electromagnetism.

Hence, the correct answer is: dynamo.

Correct answer: Voltmeter

Explanation:
A voltmeter is an electrical measuring instrument used to measure the potential difference (voltage) or electromotive force (emf) between two points in an electric circuit.

Other options:
- Ammeter: measures electric current.
- Calorimeter: measures heat.
- Barometer: measures atmospheric pressure.

Hence, the correct answer is: Voltmeter.

Correct answer: The voltage-current graph is non-linear.

Explanation:
Metallic conductors generally obey Ohm's law, which means the current through them is directly proportional to the applied voltage, provided the temperature remains constant.

As a result: - The ratio of voltage to current remains constant, which is the resistance. - The voltage-current (V-I) graph for metallic conductors is a straight line, i.e., linear. - Their resistance does change with temperature (usually increases with rise in temperature).

So, the false statement is: The voltage-current graph is non-linear.

A freely suspended magnetic compass needle aligns itself with the Earth’s magnetic field. The Earth’s magnetic field lines are roughly aligned with the north-south direction.

Therefore, the needle of the compass will come to rest along the north-south direction.

Thus, the correct answer is ”north-south direction.”