1. Connect the circuit with a compass sitting on the wire as shown in Fig. 23.10a.
2. Close the switch as shown in Fig. 23.10b. You will notice that the compass needle deflects, thereby showing a magnetic effect caused by the flowing current.
This shows the magnetic field effect of electric current.
switch compass
3. If you open the switch again, the current stops flowing and the needle returns to its normal position.
FIG. 23.10 a
b
switch compass
To demonstrate chemical effect
1. Set up a circuit as shown in Fig. 23.11. 2. You will notice bubbles forming at the electrodes. 3. Copper atoms at the anode surface lose two electrons and become part of the copper sulphate electrolyte solution as positive copper ions. This means the anode is dissolving.
4. Copper ions in the electrolyte receive electrons from the iron cathode and become metallic copper atoms again. This means the iron cathode is coated in copper.
This shows the chemical effect of current, known as electroplating.
FIG. 23.11 STS
Electroplating, or electrodeposition, has become an important industrial technique used for such purposes as protection, aesthetics and even circuit building. What began as a very rough method of coating materials is now a precise branch of science used in mass production.
To demonstrate heating effect
1. Set up the equipment as shown in Fig. 23.12. 2. Apply a constant current through the element for a constant time and record the temperature rise.
3. Keeping time and volume of water constant, apply greater amounts of current each time.
It will be seen that the temperature rise in each case will be proportional to the square of the current applied (greater current produces greater temperature rise, in the same time).
