9.1 The electric welding machine is specified as 5,3 kW, 220 V - NSC Technical Sciences - Question 9 - 2023 - Paper 1

To calculate the resistance (R) of the electric welding machine, we can use the formula:

$P = I^2R$

Rearranging gives us:

R = rac{P}{I^2}

Substituting the values, we have:

R = rac{5,3 imes 10^3}{(24,3)^2}

Calculating the resistance yields:

$R = 8,98 \, ext{Ω}$

To find the energy (W) dissipated, we use the formula:

$W = P imes t$

Where:

• P = 5,3 kW = 5,3 imes 10^3 W
• t = 30 minutes = 30 imes 60 seconds = 1800 seconds.

Substituting these values in gives:

$W = 5,3 imes 10^3 imes 1800$

Calculating this results in:

$W = 9,540,000 \, ext{J} = 9,54 \, ext{MJ}$

First, convert the energy dissipated into kWh:

W = rac{9,540,000 \, ext{J}}{3.6 imes 10^6 \, ext{J/kWh}} = 2,65 \, ext{kWh}

Now, to find the cost:

$ext{Cost} = 2,65 imes 0,75 = R1,9875$

Thus, the cost to operate the machine for 30 minutes is approximately R1,99.