02 Resistance, resistivity and Ohm’s law - Warm-Up

Resistance is defined as the​ ​ ​ (a)   ​ across a component per unit ​ (b)   of passing through it.

• potential difference
• current
• resistivity
• charge
• mass
• force
• energy
• distance

Answer explanation

This is the definition of resistance.

A current of 2.6 A flows through a 5.0 Ω resistor. Determine the electric potential difference across the resistor. Give your answer to an appropriate number of significant figures and unit.

An iron wire, with resistivity 9.71 × 10⁻⁸ Ω m, has a total length of 2.5 m and a resistance of 6.0 mΩ.

Determine the radius of the wire, in mm.

The diagram shows the I–V graph of two resistors, A and B. Identify which resistor has the greater resistance.

• A

• B

Wire X has length L and radius r. Wire Y is made of the same metal but has length 2L and radius 12⁢r.  If the resistance of wire X is R, what is the resistance of wire Y?

• 8R

• 4R

• 2R

• 0.5R

Answer explanation