1. Give the difference between the open circuit and the closed circuit.
2. List the properties of magnetic lines of force.
3. Why are some substances biodegradable and some non-biodegradable?

Hint
The circuit which is not closed and not continuous are open, the circuit which is closed and continuous are closed. The magnetic lines of force are imaginary lines which surround the magnet or the electromagnet. The substance decomposed by bacteria is biodegradable, not decomposed by bacteria is non-biodegradable.

Complete step by step answer
1. Difference between the open circuit and the closed circuit:
In an open circuit, there is no current flow in the circuit. In a closed circuit, the current flows from positive terminal to negative terminal or negative terminal to positive terminal. If the switch is in the on condition, then the circuit is closed. If the switch is in off condition, then the circuit is an open circuit.


2. The properties of magnetic lines of force:
i. The magnetic lines of force start from the north pole to the south pole of the magnet or south pole to the north pole of the magnet.
ii. The magnetic lines of force are parallel to each other.
iii. The magnetic lines of force are not intersecting with each other.
iv. All the magnetic lines of force have the same strength.
v. The magnetic lines of force are imaginary lines.
3. Biodegradable and non-biodegradable:
Biodegradable is the ability of the substance to get disintegrated by the action of the microorganisms such as the bacteria and the fungi in the presence or absence of the oxygen. The biodegradable substances are not harmful to the environment. Non-biodegradable substances are not disintegrated by the microorganisms, these substances are harmful to the environment.

Note
The current flow is not seen in the open circuit, but in the closed circuit the current flow will occur. The magnetic lines of force seen in the between the magnet to magnet or magnet to the iron and between the magnet and magnetic property of the metals. Biodegradable is the breakdown of large particles into small particles by the bacteria or fungi.