A potential difference of 2.0 V is applied across a wire of cross sectional area 2.5 mm2. The current which passes through the wire is 3.2 × 10-3 A. What is the resistance of the wire?

R = V/I = 2/3.2*10^-3

To find the resistance of the wire, you need to use Ohm's Law, which states that the resistance (R) is equal to the voltage (V) across the wire divided by the current (I) passing through the wire.

The formula for resistance (R) is:
R = V / I

Given:
Voltage (V) = 2.0 V
Current (I) = 3.2 × 10^-3 A

Now we can substitute the values into the formula to find the resistance:
R = 2.0 V / (3.2 × 10^-3 A)

To simplify the equation, we convert the current from milliamperes (mA) to amperes (A) by multiplying it by 10^-3, since there are 1000 milliamperes in 1 ampere.
R = 2.0 V / (3.2 × 10^-3 A) = 2.0 V / (3.2 × 10^-3 * 10^-3 A) = 2.0 V / (3.2 × 10^-6 A)

Now we can divide 2.0 V by 3.2 × 10^-6 A:
R = 2.0 V / (3.2 × 10^-6 A) = 6.25 × 10^5 ohms

Therefore, the resistance of the wire is 6.25 × 10^5 ohms.