Which of the following can not be charged easily by friction ?

Question

Accepted Answer

Option 4, a copper rod, is the correct answer because metals like copper are conductors of electricity. Conductors allow electric charges to move freely through them, which means they cannot hold a static charge easily when rubbed with another material. When you try to charge a copper rod by friction, any charge that is generated quickly dissipates because the electrons can move freely through the metal and into your body or the surrounding environment. This makes it difficult to maintain a static charge on a copper rod.

Now, let's examine why the other options are incorrect:

1. **A woollen cloth**: Wool is an insulator, which means it does not allow electric charges to move freely. When you rub a woollen cloth against another material, it can easily become charged by friction because the electrons are not free to move away, allowing a static charge to build up.

2. **An inflated balloon**: Balloons are typically made of rubber, which is also an insulator. When you rub an inflated balloon against your hair or a woollen cloth, it can become charged by friction. The electrons transferred during the rubbing process remain on the surface of the balloon, allowing it to hold a static charge.

3. **A plastic scale**: Plastic is another insulating material. When you rub a plastic scale with a cloth, it can become charged by friction. The electrons transferred during the rubbing process stay on the surface of the plastic, allowing it to maintain a static charge.

In summary, Option 4, a copper rod, is the correct answer because it is a conductor and cannot easily hold a static charge when rubbed, unlike the other options, which are insulators and can be charged by friction.