Paper Together: sit a paper in a room with your friends.See how it works
A second set of questions on static electricity. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
Explain why an aircraft is connected to earth with a wire before it is refuelled.
Answer: The wire lets charge flow safely to earth, so no spark can build up and ignite the fuel vapour.
Explain why the droplets from an electrostatic paint sprayer spread out.
Answer: The droplets have the same charge, so they repel each other and spread out.
A positively charged rod touches a hanging metal ball and then the ball moves away. Explain why.
Answer: The ball shares the rod’s positive charge, and like charges repel.
State how the electric field around a charged sphere changes with distance, and explain what this means for the force on a charge.
Answer: The field gets weaker with distance, so the force on a charge is smaller further away.
Short questions with options. Choose one before you open the answer.
Which particles move when an insulator is charged by rubbing?
Electrons Electrons are light and on the outside of atoms.
What is the charge on an electron?
Negative Electrons are negatively charged.
What does neutral mean when we talk about an atom?
It has no overall charge The positive and negative charges cancel out.
What charge does an object have if it has lost electrons?
Positive The object has more protons than electrons, so it is positive.
What charge does an object have if it has gained electrons?
Negative More electrons than protons gives a negative charge.
What is an insulator?
A material that does not let charge flow through it easily Plastic, rubber and dry cloth are insulators, which is why they can hold a charge.
What do two objects with the same charge do to each other?
They repel Like charges repel.
What do two objects with opposite charges do to each other?
They attract Unlike charges attract.
How does the force between two charges change as they move closer together?
It gets stronger The closer the charges, the stronger the force.
What is an electric field?
The region around a charged object where another charge feels a force The force acts without the objects touching.
What does the arrow on an electric field line show?
The direction of the force on a small positive charge Lines point away from positive charges and towards negative ones.
Which way do field lines point near a positive charge?
Away from it A small positive charge would be pushed away.
What does it mean if field lines are close together?
The field is strong there Close lines mean a large force.
What does ionised mean for air?
Electrons have been pulled off the air particles, so it can conduct Ionised air can carry charge across a gap as a spark.
What is a spark?
Charge jumping across a gap when the air ionises and conducts It happens when the potential difference gets large enough.
What does earthing do to a charged object?
It lets the charge flow away to the ground A conductor joins the object to the Earth.
Why does an earth wire need to be a conductor?
So that charge can flow along it to the ground An insulator would block the flow of charge.
Why do aircraft and tankers need to be earthed before refuelling?
So that no spark can ignite the fuel vapour Charge flows away safely instead of building up.
Why does a charged balloon stick to an uncharged wall?
It makes the nearer side of the wall the opposite charge, so they attract Unlike charges attract, and the nearer charges pull harder.
Why do charged paint droplets spread out?
They have the same charge, so they repel each other Like charges repel, which gives a fine even mist.
A student says protons move from the cloth to the rod. What is wrong?
Only electrons move. Protons are fixed in the nucleus Electrons are the particles that transfer.
A student says earthing makes an object more charged. What is wrong?
Earthing lets charge flow away, so the object ends up neutral Charge flows along the earth wire to the ground.
A positive rod touches a neutral metal ball, then the ball swings away. Why?
The ball loses electrons, becomes positive, and like charges repel Electrons move from the ball onto the rod, leaving the ball positive.
Why is the force on a charge greatest close to a charged sphere?
The field is strongest there, where the field lines are closest The field lines are closest together near the surface.
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