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Some insulating materials can become charged when rubbed together. This is because negatively
charged electrons can move from one on to the other.
When you rub a duster and polythene together, the duster becomes positively charged, and the
polythene rod becomes negatively charged. This is because the negatively charged electrons have
moved from the duster onto the polythene rod. Now, if you were to put the two near each other,
they would exert a force on to each other. Due to them being opposite charges (the duster being
positive and the rod being negative) they would attract to each other.
Now, if you were to rub the cellulose acetate rod with a duster, the duster will become negatively
charged whilst the rod will become positively charged. This is because the negatively charged
electrons will move from the rod onto the duster. If they were put near each other, they would again
attract, because the rod is positively charged, and the duster is negatively charged.
You can easily see which one is positively charged and which one is negatively charged by seeing
what the majority of the signs on the object are. For example, you can see the image below that the
majority of the signs on the duster are positive, therefore it must be positively charged.
It's important to remember that in the exam, you can be asked about any two insulating materials.
The duster and the plastic rods are just one example. You just need to apply your knowledge from
what you know about static electricity.
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Certain insulating materials can become electrically charged when rubbed against each other. This is
because negative electrons move from one object to the other.
The object which the electrons have left from becomes positively charged while the object where
the electrons move to become negatively charged
When the objects become charged, they can exert a force on to each other
If both objects are positively charged, they repel. If both objects are negatively charged, they repel.…read more
Here's a taster:
Static electricity can build up when two insulating materials are rubbed together. The friction moves
electrons from one material onto the other. This leaves a negative charge on one of the materials
and a positive charge on the other.
What charge do electrons have?
Describe how a plastic rod gains a static electric charge when you rub it
When you rub a plastic rod, the electrons can either move from the rod to the other object, making
the rod positively charged.…read more