Alice Bring Along A Silk Object.

All atoms are electrically neutral i.e. they have the same amounts of negative and positive charge inside them. The electrons carry negative charge and the protons carry positive charge. The basic unit of charge (called the elementary charge), is the amount of charge carried by one electron. The charge on a single electron is qe = 1, 6x10−19 C. All other charges in the universe consist of an integer multiple of this charge (i.e. Q = nqe). This is known as charge quantisation. All the matter and materials on earth are made up of atoms. Some materials allow electrons to move relatively freely through them (e.g. most metals, the human body). These materials are called conductors. Other materials do not allow the charge carriers, the
They have a small neutral ball wrapped in tin foil attached to a piece of string and a Perspex ruler. Alice brings along a silk cloth.

Explain the difference between a charged object and a neutral object. (2) Write down a possible investigative question. (2) Write down a possible hypothesis. (2) Name at least ONE variable that must be controlled during this investigation. (1)

Alice rubs the Perspex ruler with the silk cloth to give it a negative charge.

Were electrons added to or removed from the Perspex ruler during this process? (1) Is the ruler an electrical conductor or insulator? Explain your answer. (2)

Alice then brings the ruler close to the ball without touching it. She notices that the ball is attracted to the ruler.

Explain why the ball is attracted to the ruler. What is the name of this process? (3) Draw a sketch showing how the charge is distributed on the surface of the ball. (3) Provide ONE example of where this electrostatic attraction is used in everyday life and an advantage of its use. (2) [18]

Things that I am unsure
Its voltage-current graph does not follow a straight line. Instead, it gives a curve with an increasing gradient. It shows that the resistance increases as the current increases.

An ohmic conductor is a component that obeys Ohm’s law. A graph of voltage on the vertical axis against current on the horizontal axis (a voltage-current graph) gives a straight line with a positive gradient. The steeper the gradient, the higher the resistance will be.

What causes resistance? Metals are good conductors of electricity. The structure of metals consists of positively charged metal ions surrounded by a ‘sea’ of negatively charged electrons.

The electric current in a metal conductor such as a wire is the flow of electrons through the metal. The electrons are the charge carriers in a metal. Electrical resistance is due to these charge carriers colliding with metal atoms as they flow through the