Magnetism and Electricity Movement Between Charges
As we know, movement suggests that a force is being exerted. This force has a magnitude and direction (it is a vector) and its direction depends on the types of charges involved.
There are two types of static charges: positive charges (+) and negative charges (–). These charges can attract or repel each other in much the same way as the poles of magnets.
z A negative charge repels a negative charge: these are the same type of charge, or like charges.
z A negative charge attracts a positive charge: these are the opposite type of charge, or unlike charges.
z A positive charge repels a positive charge: these are the same type of charge, or like charges.
Like charges repel. Unlike charges attract.
Explaining charging
Using your knowledge of subatomic structure and the balance of protons and electrons in atoms, show the electron configuration for a sodium atom that has lost two electrons. How does this explain why items that lose electrons become positively charged?
18.3
Repel Fig. 18.3.2 How like and unlike charges interact Electric water
1. Turn on a tap in the laboratory so that a thin stream of water flows.
2. Rub a polythene rod off your jumper (rubbed polythene becomes negatively charged).
3. Bring the rod close to the stream of water.
4. Repeat this task using a piece of cellulose acetate (an overhead projector plastic sheet). This takes on a positive charge when rubbed.
5. Record your observations. What do these results tell you about the charges present in water?
Charges – moving or not?
Using your knowledge of the subatomic structure, draw a diagram to explain the statement: ‘In static electricity, it is only the negative charges that move’.
