Download Electrical energy and voltage

Electrical energy and voltage
Voltage is a measure of the energy of the electricity.
Each coulomb of electricity that flows from a battery has some energy. The voltage of the
battery tells us just how much energy. So if one coulomb of electric charge flows from a 240
V source, it will have more energy than one from a 12 V source.
We can compare voltage with gravitational (potential) energy in the pictures below.
Energy out: Heat and light
Energy out: Kinetic
Figure 1
Energy in: Lift
Energy in: Battery
If a given amount of mass travels down
the hill, say one truck load, the energy lost
depends on the height of the hill; the
higher the hill the more energy is lost. The
height is measured from the top to the
bottom of the hill.
If a given amount of electricity flows from
a battery, say one coulomb, the energy
lost depends on the voltage of the battery;
the greater the voltage the more energy is
lost. Voltage (properly called potential
difference) is measured between two
places in the circuit.
The potential difference (voltage) is measured between two points on the circuit with a
voltmeter. It is really measuring the loss of energy of the electricity between one point and
the other.
This is shown by the diagrams in Figure 2. The reading of V1 in the first circuit shows how
much energy is lost in the bulb - it is turned into heat and light. The reading of V2 will be 0, as
almost no energy is lost in the connecting wires.
In the second circuit the battery is supplying energy to two bulbs. If the bulbs are identical
the energy lost in one will be the same as the energy lost in the other.
Using the figures in the diagram there will be a 3 V drop across each bulb.
In the third circuit one bulb is much more powerful than the other, there is much more energy
used in it and so the voltage drop across it is large compared with the other bulb.
V2
3V
9V
6V
V1
3V
12V
3V
Figure 2