15081 Experiment Pack - Electric Circuits - info

 EXAMPLE EXPERIMENTS

(all worksheets have necessary diagrams)

11. CURRENT REGULATION

In order to control the current that flows in a load, for instance a bulb, we can use a rheostat.

Arrange the circuit illustrated in the following picture.

The rheostat is arranged so that by rotating the knob, the resistance may be varied from a minimum of 0 to a maximum of 22 ohm.

With the potentiometer completely turned towards one end, watch the ammeter’s indication and the brightness of the lamp. Turn the knob slowly, while watching the effects of the resistance changing.

12. THE POTENTIOMETER

The rheostat can be used as voltage control instead of a current control.

In such a configuration it is called a potentiometer. As you can see in the following picture the rheostat has one end to the positive terminal and the other end to the negative terminal. The slider takes off the current at an intermediate point of the resistance, so it may be at a voltage between 6v and 0V.

Turn the knob slowly and observe the effect of the change of resistance.

13. RESISTORS IN SERIES

When two resistors are connected in series, the current that passes through them is necessarily the same. We will see how the voltage is distributed between the resistors, referring to Ohm’s Law.

Arrange the following circuit and supply it with a 6V voltage.

Write the current value that flows in both resistors. For each of them apply Ohm’s Law, calculating the value of the voltage between their ends. For instance if the current is of 0.2A and it flows in a 12ohm resistor, as V=R*1, at its ends there should be a voltage of 0.2*12=2.4V.