Resistance

The idea

Every conductor offers some opposition, or resistance, to the flow of current, and different conductors offer different resistance; nichrome offers more than copper of the same size and length.

Two wires, same size

Take a copper wire and a nichrome wire of the same size and length. Join each to a cell, one after the other.

Which wire do you think makes it harder for current to flow?

• Nichrome
• Copper
• Both exactly the same

Compare the wires

Choose the copper wire and the nichrome wire. Look at the resistance label each time.

Some oppose more

Both wires let current flow, but they do not oppose it equally. Nichrome has the higher resistance.

Every conductor offers some opposition, called resistance, to the flow of current. Different conductors offer different resistance. A nichrome wire offers more resistance than a copper wire of the same size and length.

• Wire (same size and length) | Resistance
• Copper | Lower
• Nichrome | Higher

Notes

Every conductor offers some resistance to the flow of current, and different conductors offer different resistance. Nichrome offers more than copper of the same size and length.

Check yourself

The opposition a conductor offers to the flow of current is called …

A copper wire and a nichrome wire have the same size and length. Which has the higher resistance?

Do all conductors offer the same resistance to current?

• insulation. An insulator does not let current flow. Resistance is the opposition inside a conductor.
• magnetism. Magnetism is about magnets. The opposition to current is resistance.
• resistance — correct. Yes!
• Copper. Nichrome offers higher resistance than copper.
• Nichrome — correct. Yes!
• They are always exactly equal. Different conductors offer different resistance.
• Yes, all offer exactly the same. Different conductors offer different levels of resistance.
• No, different conductors offer different resistance — correct. Yes!
• No, some offer no resistance at all. Every conductor offers some resistance.