You will need:
1. Tape the can to the aluminium foil.
2. Cut two strips of aluminium foil, approximately 4cm x 0.5cm.
3. Make a hook on the end of each aluminium strip. Hang the strips of the end of the ring pull tab.
4. Place the electroscope near your TV. What happens to the strips? Why?
5. Try charging up a balloon by rubbing it with cloth. Bring it near the electroscope... what happens?
Like charges repel each other, opposite charges attract each other. As you rub the electroscope, electrical charges from the Aluminium can come down to the Aluminium foil leaves, which then repel each other as they have the same charge (this will either be positive or negative).
As you put this near other statically charged objects (eg. a TV), you'll see movement of these charged strips. Depending on whether the aluminium strips are attracted or repelled to the appliance, you can tell whether the static from an appliance is positively charged or negatively charged. If an object with the opposing charge is brought near the electroscope, the strips of Aluminium leaves will hang straight down. The strips no longer repel each other because the charge has been discharged.
The electroscope can also be charged by electrostatic induction, whereby you can bring a charged object is brought near the electroscope; this will make the leaves also diverge as well because the electric field of the object causes the charges in the electroscope rod to separate.
A loss of electrons makes an object positively charged,
a gain of electrons makes an object negatively charged.