Part-II

Question 1

In a circuit, the bulb does not glow. Give possible reasons.

Answer 1

• The wires and loosely connected
• Bulb is fused
• Cells are used up
• Liquid is an insulator

Question 2

Why does a fireman shut of the electrical supply before using a water hose?

Answer 2

Water used is not pure water and is a good conductor of electricity. So they shut it off in order to save themselves and others from electrocution.

Question 3

The free end of a tester is dipped into a solution and the magnetic needle shows deflection. Why?

Answer 3

It shows that the circuit is complete and the solution conducts electricity. (It is a good conductor)

Question 4

Does pure water conduct electricity. If not how can we make it?

Answer 4

No. If salt is dissolved in it, it conducts electricity.

Question 5

Nam 3 liquids when tested cause the magnetic needle to deflect.

Answer 5

• Vinegar
• Tap Water
• Lime Juice

Question 6

Compass needle deflects more in seawater than in drinking water. Why?

Answer 6

Seawater contains more salt and therefore is a better conductor. It produces a stronger magnetic field causing the needle to deflect more.

Question 7

What is an electrolytic cell?

Answer 7

The process of electrolysis takes place in a device called an electrolytic cell.

Question 8

LED

Answer 8

• Light Emitting Diode
• glows even with a weak current flowing through it
• longer lead is connected to the positive terminal and the shorter lead is connected to the negative terminal of the battery

Question 9

What are the chemical effects during passage of electricity?

Answer 9

• Bubbles of gas formed on the electrodes
• Deposit of metals on electrodes
• Change in colour of the solution