Electric Circuits Flashcards
(30 cards)
Why does an atom have no charge?
It has an equal numbers of positive protons and negative electrons.
What happens when electrons are removed from an atom?
It becomes positively charged
What happens when electrons are added to an atom?
It becomes negatively charged
When can insulating materials become charged and why?
When they are rubbed with another insulating material. This is because electrons are transferred from one material to another.
What is electric charge measured in?
Coulombs (C)
What does a charged object create around it?
An electric field
When a charged object is placed inside an electric field, what happens?
The object experiences electrostatic attraction
What sort of force is electrostatic attraction?
Non-contact
As the distance between the two objects decreases, what happens?
The electric field and the force between the objects increases
How does a spark happen?
- If two objects have a very strong electric field between them, electrons will be strongly attracted toward the positively-charged object.
- If the field is strong enough, electrons will be pulled away from the air molecules and cause a flow of electrons between the objects
What is the unit of current?
Amp (A)
In circuit diagrams, where does current flow from and to?
The positive terminal of a cell or battery, to the negative terminal -> conventional circuit
Circuits: In a single closed loop, what is the same throughout the whole circuit?
The current
Why are metals good conductors of electricity?
They contain delocalised electrons, free to flow throughout the structure, which can carry a charge
What is potential difference a measure of?
How much energy is transferred between two points in a circuit
What is the unit of p.d.?
Volt (V)
What is the p.d. across a component equal to?
Each coulomb of charge that passes through it
What is the p.d. across a power supply/battery equal to?
The energy transferred to each coulumb of charge that passes through it
What must there be for an electrical charge to flow through a circuit?
A potential difference
What is resistance caused by?
When electrons move through a circuit, they collide with the ions and atoms of the wires and components in the circuit.
What is the unit of resistance?
Ohms (Ω)
Why would a longer wire have more resistance than a shorter wire?
Electrons collide with more ions as they pass through a longer wire
What does the line look like on a current-p.d. graph of an ohmic conductor?
Straight
What does the line look like on a current-p.d. graph of a filament lamp?
An ‘S’ shape
