Electricity Flashcards
WHAT CHARGES ATTRACT AND REPEL
positive + positive = repel
negative + negative = repel
positive + negative = attract
WHAT IS ELECTRIC CURRENT
The electric charge transferred per unit time.
WHATS A CONDUCTOR AND INSULATOR
Conductor - Something that allows electrons to move freely - metals.
Insulator - Somethinv thag doesn’t allow electrons to move freely - wood
WHAT IS ALTERNATING CURRENT (A.C)
Flow of electrons regularly changes direction.
The voltage varies from 0 to peak voltage in one direction then back to 0 then to peak voltage in the opposite direction e.g mains power
WHAT IS DIRECT CURRENT (D.C)
The electrons flow around the circuit in one direction
The voltage remains constant eg battery power.
WHAT DO CHARGED PARTICLES HAVE AROUND THEM
Electric fields apply a force to them and make them move. The path it follows depends on the electric field.
A charged particle experiences a force in an electric field.
TWO OPPOSITELY CHARGED PLATES
A proton would move towards the negative plate.
- Always use a positive charge to determine field lines.
- Closer field lines = Stronger charge.
- Curved lines at end.
Parallel lines - field is uniform (the same)
POINT CHARGE
(RADIAL FIELD)
Positive charge placed in the field would move away.
TWO OPPOSITELY CHARGED POINTS
If a positive charge was placed on the field lines, it would move towards the negative point.
TWO LIKED CHARGE POINTS
If a positive charge was placed on the field lines, it would move away following the curved lines.
WHAT IS POTENTIAL DIFFERENCE (VOLTAGE)
Potential difference measures how much energy the supply gives to each coulomb of charge.
9V battery means 9 joules to each coulomb.
SERIES CIRCUIT RULES
- Only has one loop and everything would be turned off if there was a break in the circuit or a switch is switched.
- The voltage adds up to the supply and the current is the same throughout all points.
PARALLEL CIRCUIT RULES
- Has multiple branches.
- The currents add up to the supply current and the current increases as more branches are added.
- The voltages are the same at all points.
- A break in the circuit only affects the broken branch.
WHAT IS RESISTANCE
Anything in a circuit resists and the more it resists the higher its resistance.
Opposes current
Resistance in series = RT=R1+R2+R3…
If more resistors are added in series, the current decreases. (resistance increases).
Resistance in parallel = 1/RT=1/R1+1/R2+1/R3…
If more resistors are added in parallel, the current increases (resistance decreases).
WHAT IS OHMS LAW
Ohms law is the relationship between potential difference and current. This leads to the idea of resistance.
WHAT IS THE OHMS LAW EXPERIMENT
How does the potential different across a resistor affect the current in the resistor.
Vary the potential differences across the resistors by turning the control on the power supply. Record the current in the resistors at different potential differences.
Straight line through origin. Voltage is directly proportional to current.
The gradient of a VI graph is the value of resistance.
Ohmic conductors obey ohms law. Straight line and a positive gradient.
Non-ohmic conductors don’t obey ohms law eg bulb. It follows a curved line with an increasing gradient. Resistance increases as the current increases.
WHY DOES RESISTANCE INCREASE WITH TEMPERATURE
Example: filament wire of a bulb.
As the voltage increases, the wire heats up. This makes the atoms in the wire vibrate more which makes it difficult for the electrons to move along the wire - resistance increases.
Old fashioned filament lights always pop when turned on because the current will be higher when put on and is more likely to break as the resistance will be lower.
WHATS A CELL AND SYMBOL
Produces electrical energy