Final answer:
To calculate the heat produced by two resistors in series across a 220V supply, add their resistances, use Ohm's law to find the current, calculate power using P = I²R, and then find the energy by multiplying power by the time in seconds.
Step-by-step explanation:
To find the heat produced by a combination of resistors in series across a 220V supply, you can use the formula for electrical power (P = VI) and the fact that power is the rate at which energy is converted (P = E/t), where E is energy in joules and t is time in seconds. When resistors are in series, their resistances add up to form the total resistance (R = R1 + R2). For resistors of 40 ohms and 60 ohms in series, the total resistance (Rtotal) is 100 ohms.
Applying Ohm's law (V = IR), we calculate the current (I) through the circuit as I = V/Rtotal = 220V / 100Ω = 2.2A. Now, using P = I2Rtotal, we find the power as P = (2.2A)2 × 100Ω = 484W. To find the heat produced (E) in half a minute (30 seconds), we use E = P × t, resulting in E = 484W × 30s = 14520J, which is the amount of heat produced in joules.