a] State Ohm's law. Write it in the form of equation and give graphical representation for it.
b] An electric oven rated at 500W is connected to a 220V line and used for 2 hours daily. Calculate the cost of electric energy per month at the rate of Rs. 5 per kWh.

Explanation

a] Ohm.s Law: Current through a conductor between two points is directly proportional to the voltage across the two points.
Mathematically,
`VpropI`
or V = RI
where R is the constant of proportionality called resistance.

If a graph of current across a conductor along y-axis is plotted against the potential difference across it taken along x-axis for different values of potential difference, then, it looks as shown in the figure. The graph will be a straight line which confirms that potential difference V is directly proportional to current I according to Ohm.s law.
b] Power of the oven [P] = 500 W = 0.5 kW
t[time] = 2hrs
E = `Pxxt=0.5xx2=1kWh`
Energy consumed in 1 month = `1kWhxx30=30kWh`
1 kWh = Rs. 5
Cost for 30 days = `5xx30` = Rs. 150.00