3a) A 2A electrical heater was connected to a 110V supply for 1 hour. Calculate the cost of running the electricity electric heater. b) State one limited limitation of the ohms Ohion's law. c) Name the two cables on a pin plug.

$$P = V \times I$$ $$P = 110 \text{ V} \times 2 \text{ A}$$ $$P = 220 \text{ W}$$

$$P = \frac{220 \text{ W}}{1000}$$ $$P = 0.22 \text{ kW}$$

$$E = P \times t$$ $$E = 0.22 \text{ kW} \times 1 \text{ hour}$$ $$E = 0.22 \text{ kWh}$$

(Assuming electricity cost is $0.15 per kWh).

$$\text{Cost} = E \times \text{Cost per kWh}$$

$\text{Cost} = 0.22 \text{ kWh} \times \$0.15/\text{kWh}$ $\text{Cost} = \$0.033$ The cost of running the electric heater is \boxed{\text{}\0.033}$

b) One limitation of Ohm's Law is that it only applies to ohmic materials (like most metals) where resistance remains constant regardless of the voltage or current. It does not apply to non-ohmic devices (e.g., diodes, transistors, or thermistors) where the resistance changes with voltage or current, or if physical conditions like temperature change significantly.

c) The two cables on a 2-pin plug are the:

• Live wire
• Neutral wire