Chemical effect:

We can show that electric current produces chemical effect by testing with potato.

When we insert the copper wires of tester in a potato cut half, after sometime we will observe a greenish spot around the wire connected to positive terminal of battery.

This is because current has caused a chemical reaction in the potato

Heating effect:

we can show that electric current produces heating effect by connecting the ends of our tester with an electric bulb.

Due to heating effect of current, the filament of the bulb gets heated to a high temperature and it starts glowing.

Magnetic effect:

When a compass needle is kept nearby a wire carrying electric current the needle in the compass undergoes deflection even if the current is weak. This deflection is produced due to magnetic effect of current.