The figure shows a person holding a polythene strip after it has been rubbed with a duster cloth. The strip acquires a negative charge. Yet, after a few seconds, the duster cloth does not show any charge. Which of the following could be the reason for this?

The following experiment was conducted in the physics laboratory. A wooden pencil is sharpened at both ends. It is connected to two bulbs and a battery as shown. The two crocodile clips are connected to the wooden part of the pencil.

Students noticed that the bulbs do not light up. Why do the two bulbs not light up?

Akhil and friends have made the following circuit. Two crocodile clips are connected to the lead or graphite of the pencil as shown. The two bulbs connected to the circuit will light up dimly. Why do the two bulbs light up?

A conductor is a material that allows electricity to flow through it. An Insulator is a material that electricity cannot flow through. 
To determine whether an object is a conductor or insulator, you can build a simple circuit with a battery, light bulb, and three pieces of wire. 

Touch the free ends of the wire to the object you are testing. If the light bulb lights up, the object is made from a conductor. If it does not, the object is made from an insulator. 

We can easily draw electrical circuits by following some simple rules.

1. Use a ruler to draw straight lines to represent the wires.

2. Use the correct circuit symbols to represent different components.

3. Ensure that the circuit is closed and has no gaps. 

Write down as many things as possible that is wrong with the circuit below? 
 

Sulphur is an electrical insulator, but it can be made to conduct electricity if a very bright light shines on it. A very bright light shines onto a small circular area in the centre of the charged slab of sulphur. The pattern of charge on the sulphur alters. The simplified diagram represents the new pattern of charge.

Explain why the pattern alters in this way.