Question

An electric lamp of resistance 400 ohms is connected to a supply of 200V. The lamp is used for 20 hours a day. If the rate per unit is Rs 2 find the cost of using this lamp for the month of April.(30days)

Answer 1

• Voltage=V=200V
• Resistance=R=400ohms
• Time=t=20h

We know

$\boxed{\sf Energy=E=\dfrac{V^2}{R}t}$

$\\ \sf\longmapsto E=\dfrac{200^2}{400}\times 20$

$\\ \sf\longmapsto E=\dfrac{40000}{400}\times 20$

$\\ \sf\longmapsto E=100(20)$

$\\ \sf\longmapsto E=200KwH$

$\\ \sf\longmapsto E=200units$

• Rate per unit=2
• Days=30

$\\ \sf\longmapsto Bill=2(30)$

$\\ \sf\longmapsto Bill=Rs60$