*With the increasing pressure towards energy efficiency, many are wondering how much power a light bulb actually uses. To answer this question, you must take some measures. According to the equation Power = Voltage x Current, if you know the voltage and current you can determine the power. The voltage must be measured in volts and the current must be measured in amps in this equation to work properly. Then the unit will have units of watts, and the volts for the amps equals one watt.*

*With the increasing pressure towards energy efficiency, many are wondering how much power a light bulb actually uses. To answer this question, you must take some measures. According to the equation Power = Voltage x Current, if you know the voltage and current you can determine the power. The voltage must be measured in volts and the current must be measured in amps in this equation to work properly. Then the unit will have units of watts, and the volts for the amps equals one watt.*

### Step 1

Place the power supply on the table. Make sure the power outlet is close. Place the bulb in the socket of the socket. Cut two 12-inch (30.48 cm) pieces of black thread. Peel 1/2 inch (1 cm) of insulation at the ends of each wire.

### Step 2

Connect the negative terminal of the power supply to one of the two terminals in the light bulb socket using one of the two black wires. Connect one end of the second black wire to the second terminal of the light bulb socket.

### Step 3

Connect the other end of the second black wire to the black negative wire of the digital multimeter. Connect the red probe cable from the digital multimeter to the positive terminal of the power supply.

### Step 4

Adjust the digital multimeter to measure the current in amps. This adjustment is usually indicated by “10A”. Turn on the multimeter and connect the power supply. Turn on the power supply and increase the supply voltage to 12 volts. Record both the 12 volt voltage reading and the current reading displayed on the digital multimeter. If the current reading is 1.5 amps, write that, for example.

### Step 5

Multiplies the voltage and current readings. For example, 12 volts per 1.5 amps equals 18 watts. This is the amount of power the bulb is using.

References