Final answer:
To calculate the increase in current when resistance decreases, apply Ohm's law. With a constant voltage of 240 V and resistance dropping from 40 ohms to 30 ohms, the current increases from 6 A to 8 A, resulting in an increase of 2 A.
Step-by-step explanation:
If the voltage of a circuit stays constant at 240 V and the resistance of the circuit changes from 40 ohms to 30 ohms, we can find the change in the circuit's current by using Ohm's law. Ohm's law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. The formula for Ohm's law is I = V/R.
Initially, with a resistance of 40 ohms, the current is I1 = V/R1 = 240 V / 40 ohms = 6 A.
After the resistance changes to 30 ohms, the new current is I2 = V/R2 = 240 V / 30 ohms = 8 A.
The increase in current can be calculated as ΔI = I2 - I1 = 8 A - 6 A = 2 A. Therefore, the circuit's current will increase by 2 A.