Electrical Power and Energy

When a battery sends a current through a resistor, as in Fig. the battery is furnishing energy to resistor. In effect, the battery lifts charge from the low potential at b to higher potential at a. the potential difference between these two points is simply the voltage of the battery. The work done by the battery in the process of lifting a charge q from b to a is,

Let us next compute the power output of the battery as it drives a current rough the circuit. We have known at 8th grade that

Power = W (P) t

P = V I

By using Ohm’s Law (V = IR) Prove that can express with

P = IRI = I2 R P = watt (J/s)V = voltR = ohm

W = Joule t = second Q =coulomb

Factor that can influence the magnitude the powerVoltage , Resistance, Current, Time, charge

Power in electrical devices

How to calculate Energy?

R

Voltage resourceo o

I

• Electrical Energy’s signed by E•The unit (SI) is watt seconds E = P t E= V.I.t E = I2Rt (Because V = IR)

KWh meter, use to measure electrical Energy

Electric Stealing

CALCULATE ELECTRIC COST

Cost = Energy x tariff rate = KWh x tariff rate (in Rupiah)

Exercises

1. In a house , there are 5 lamps of 60 watt each, a TV of 70 watt. If those electric devises are Turned on for 4 hours every day, what is the cost that must be paid for 1 month (30 days) If price of 1 kWh = Rp 100.00

2. A TV turned on for 10 hours per day, is connected to a voltage of 220 V and needs current Of 3 A. If the price of 1 kWh = Rp 200.00, calculate the electricity cost that must be paid for 1 month ( 30 day)