Static Electricity Flashcards
All 23 cards in this deck
Which type of materials become electrically charged when they are rubbed against each other?
Certain insulating materials.
Which particles are transferred when two insulating materials are rubbed together?
Electrons, which are negatively charged.
What charge is left on a material that gains electrons when rubbed?
A negative charge.
True or false? Rubbing a cloth on a rod transfers positive charge from the cloth to the rod.
False. Only electrons (negative charge) are transferred; positive charges do not move.
True or false? A cloth that loses electrons is left with an equal positive charge.
True. The charge lost by one material equals the charge gained by the other.
What are the steps to explain why a material becomes positively charged by rubbing?
e.g. a cloth rubbed on a polythene rod becomes positively charged
- Electrons are transferred from the cloth to the rod.
- Electrons are negatively charged.
- So the cloth has more positive charges than negative charges — it is positively charged.
What force acts between two objects that carry the same type of charge?
They repel each other.
What force acts between two objects that carry different types of charge?
They attract each other.
What type of force is the attraction or repulsion between two charged objects?
A non-contact force.
True or false? Two charged objects must touch before they exert a force on each other.
False. Charged objects exert forces on each other without contact — the force is a non-contact force.
What is observed when a charged rod is brought near a suspended rod carrying the same type of charge?
The suspended rod swings away without being touched — evidence of a non-contact repulsive force.
A negatively charged rod lies on a balance and a second negatively charged rod is held above it without touching. What happens to the balance reading, and why?
The reading increases — like charges repel, giving an additional downwards force on the rod on the balance.
What is an electric field?
The region around a charged object where another charged object experiences a force.
How does electric field strength vary with distance from a charged object?
It is strongest close to the object and gets weaker as distance increases.
What does the electric field pattern around an isolated charged sphere look like?
Straight lines spread out evenly all around the sphere (radial lines), drawn from the centre outwards.
Which way do electric field lines point around a charged sphere?
Away from a positively charged sphere, towards a negatively charged sphere.
True or false? The electric field around an isolated charged sphere is drawn as circles going round the sphere.
False. The field lines are straight and radial, pointing directly in to or out of the sphere.
What happens to the force on a charged object as it is moved closer to another charged object?
The force gets stronger, because the field is stronger closer to the charged object.
What are the steps to explain why a spark jumps between a charged object and an earthed conductor?
e.g. a negatively charged rod held near an earthed metal conductor
- The large potential difference creates a strong electric field, so the air breaks down (ionises).
- Electrons move through the air — there is a current in the air.
- They move from the rod to the earthed conductor, seen as a spark.
What happens to air when the electric field around a charged object becomes very strong?
The air becomes ionised (breaks down) so it conducts charge.
How can a person flying a kite very close to (but not touching) an overhead power cable receive a shock?
The electric field strength is very high, so the air is ionised and conducts charge through the kite and string to the person/earth.
A student touching a negatively charged dome finds her hair stands on end. What causes this?
Electrons are transferred to her, so each hair is negatively charged, and like charges repel.
As the distance between a charged object and earth increases, what happens to the potential difference needed for a spark to jump?
It increases.
A bigger gap needs a bigger potential difference before the air breaks down and conducts.