Paper1_electricity_physics Flashcards
What do circuit symbols show
Circuit symbols show components in a circuit and how they are connected
Define current
Current is the rate of flow of charge in a circuit
What is potential difference
Also know as voltage is the difference in potential charge/energy between two points of a circuit, which causes a current to flow
Define charge
Charge is the amount of electricity travelling through a circuit
What is resistance
Resistance is anything that shows the flow of charge around a circuit, usually caused by electrons colliding with ions in a material
What is a series circuit
A circuit with a single loop of wire
What is a parallel circuit
A circuit with two or more loops (branches) of wire
What must there be in a closed circuit for a charge to flow
For electrical charge to flow through a closed circuit the circuit must include a source of POTENTIAL DIFFERENCE
What is an electric current
The flow of electric charge, normally electrons around a circuit
What is the same at any point in a series circuit
In a series circuit the CURRENT is the same at any point of the loop
What is the formula for charge flow
Charge flow(c)= current (a) x time (s)
Q=It
What affects the current through through a component
The current through a component depends on the RESISTANCE of the component and the POTENTIAL DIFFERENCE across the component
What happens if the current is smaller than the resistance
The greater the resistance of a component THE SMALLER THE CURRENT FOR A GIVEN POTENTIAL DIFFERENCE ACROSS THE COMPONENT
What is the formula for potential difference
Potential difference(v)= current(a) x resistance
V=IR
What affects resistance
Resistance depends on the COMPONENTS AND LENGTH OF THE WIRE USED
What happens if the wire is longer
The longer the wire THE GREATER THE RESISTANCE
What is the name given to resistors that have a fixed value
Some resistors have a fixed value which doesn’t depend on the current flowing through the circuit, they are called OHMIC CONDUCTORS
What does the Ohm’s law state
THE CURRENT THROUGH AN OHMIC CONDUCTOR ( AT A CONSTANT TEMPETATURE) IS DIRECTLY PROPORTIONAL TO THE POTENTIAL DIFFERENCE ACROSS THE RESISTOR
What do you see on a graph when results are taken from an ohmic conductor
Ohmic conductors PRODUCE A STRAIGHT LINE which goes through the origin
What happend if the current increases in a filament bulb
As the current increases THE TEMPERATURE OF FILAMENT INCREASES THEREFORE THE RESISTANCE OF THE FILAMENT LAMP INCREASES
Name a non-ohmic conductor
FILAMENT LAMP
Name objects where the resistance is not constant
The resistance of components such as LAMPS, DIODES, LDR’S is not constant ,it changes with the current through the component
Describe the features of diodes
diodes are electrical components THAT ONLY ALLOW A CURRENT TO FLOW IN ONE DIRECTION, HAVE LOW RESISTANCE IN THE FORWARD DIRECTION BUT A HIGH RESISTANCE IN THE REVERSE DIRECTION
Describe LDR’s
LDR’s are types of resistors where THE RESISTANCE VARIES WITG LIGHT INTENSITY, RESISTANCE DECREASES AS LIGHT INTENSITY DECREASES
Where are LDR’s used
USED IN SWITCHES TO TURN STREET LIGHT ON WHEN IT GETS DARK
What is one formula for power
POWER/RESISTANCE (R) = POTENTIAL DIFFERENCE (V) X CURRENT (I)
P=VI
Name the other formula for power
POWER (P) = CURRENT^2 (I) X RESISTANCE (R)
P= I^2 R
What can be added to get a range of potential differences and currents
To get a range of potential differences and currents a VARIABLE RESISTOR CAN BE ADDED TO THE CIRCUIT OR THE INPUT POTENTIAL DIFFERENCE CHANGED
Describe a series circuit
SAME CURRENT THROUGH EACH COMPONENT, TOTAL POTENTIAL DIFFERENCE OF THE POWER SUPPLY IS SHARED BETWEEN THE COMPONENTS, TOTAL RESISTANCE OF THE TWO COMPONENTS IS THE SUM OF RESISTANCE OF EACH COMPONENT
Describe parallel circuits
POTENTIAL DIFFERENCE ACROSS EACH COMPONENT IS THE SAME, TOTAL CURRENT THROUGH THE SEPERATE COMPONENTS ON EACH LOOP, TOTAL RESISTANCE OF TWO RESISTORS IS LESS THAN THE RESISTANCE OF THE SMALLEST INDIVIDUAL RESISTOR
What does a direct potential difference produce
A direct potential difference produces A DIRECT CUREENT
What is a direct current
A direct current (dc) is A CURRENT IN WHICH THE CHARGE CARRIERS MOVE IN ONE DIRECTION
Give an example of an object that has a direct current
BATTERIES
What will an alternating potential difference produce
An alternating potential difference WILL PRODUCDE AN ALTERNATING CURRENT
What is an alternating current (ac)
A CURRENT IN WHICH THE CHARGE CARRIES MOVE BACK WARDS AND FORWARDS
Give an example of a thing that uses an alternating current
MAINS ELECTRICITY
What happens to the demand of electricity during adds
Mains supply changes slightly which is why WHEN ADDS ARE ON DURING A BIG SHOW LOTS OF PEOPLE PUT THE KETTLE ON SO DEMAND INCREASES
What does the brown wire do
BROWN, LIVE WIRE, CARRIES ALTERNATING POTENTIAL DIFFERENCE FROM THE SUPPLY
What does the blue wire do in a plug
BLUE, NEUTRAL, COMPLETES THE CIRCUIT
What is the function of the yellow/ green wire
YELLOW/GREEN, EARTH WIRE, SAFETY WIRE TO STOP APPLIANCE COMING LIVE earth wire is at 0v
What does the earth wire do if there is a fault
THE EART WIRE CARRIES A CURRENT if there is a fault
Why is the live wire (brown) dangerous
The live wire may be dangerous as WHEN A SWITCH IN THE MAINS CIRCUIT IS OPEN A PERSON COULD COMPLETE THE CIRCUIT TO THE GROUND AND GET ELECTROCUTED as the current will flow through them
What happens if the live wire and earth wire inside a plug touch
Any connection between the live wire and earth wire CAN CAUSR A CURRENT TO FLOW, POTENTIALLY CAUSING A FIRE ( IF CURRENT IS TOO HIGH) OR ELECTROCUTION IF A PETSON MAKES THE CONNECTION
What is the power rating of an appliance
THE RATE AT WHICH ENERGY IS TRANSFERRED TO THE APPLIANCE
What do electrical appliances do
Electrical appliances CONVERT ELECTRICAL ENERGY from ac mains or batteries INTO MORE USEFUL FORMS
What do lightbulbs do with electrical energy
Lightbulbs CONVERT ELECTRICAL ENERGY INTO LIGHT ENERGY
What are the formulas for work done
ENERGY TRANSFERRED (J) = POWER (W) X TIME (S) E=Pt
ENERGY TRANSFERRED = CHARGE FLOW (C) X PD (V) E=QV
What is the national grid
The national grid is A SYSTEM OF CABLES AND TRANSFORMERS LINKING POWER STATION TO CONSUMERS
What is the role of the step up transformer
Step up transfromet is USED TO INCREASES THE POTENTIAL DIFFERENCE FROM THE POWER STATION TO THE TRANSMISSION CABLES AND DECREASE CURRENT
What do the steps down transfromers do
Step down transformers are USED TO DECRESE THE POTENTIAL DIFFERENCE TO A MUCH LOWER VALUE FOR DOMESTIC USE IN HOMES AND INCREASE CURRENT
What does the electric current generate when it moves through electrical wires
Electric current generates HEAT as it moves through electrical wires
Why is electricity transmitted at a very high potential difference and low current
When electricity is transmitted at a very high pd and low current it means LESS ENRGY IS WASTED MAKING THE SYSTEM MORE EFFICIENT
Why is a lower potential difference used in the home
AS IT IS SAFER
What are pylons for
PYLONS CARRY OVERHEAD POWER CABLES WHICH CONTAIN THE HIGH VOLTAGE ELECTRICITY FROM WHERE IT WAS GENERATED
Why are step up transformers used
INCREASING PD WILL DECREASE CURRENT, LOWER CURRENT MEANS LESS HEATING OF THE POWER CABLES, LESS ELECTRICAL ENERGY WASTED AS HEAT, MAKES TRANSMISSION PROCESS MORE EFFICIENT
Name the two types of charges
POSITIVE (+) and NEGATIVE (-)
What happens when two electrical charges are placed near each other
When two electrical charges are placed near each other THEY EXERT A FORCE ON ONE ANOTHER the direction of the force depends on the electrical charges
Are electrostatic forces contact or non-contact
Electrostatic forces are an example of NON-CONTACT FORCES
Explain friction
When certain INSULATING MATERIALS ARE RUBBED TOGETHER THEY BECOME ELECTRICALLY CHARGED, NEGATIVELY CHARGED ELECTRONS ARE RUBBED OF ONE MATERIAL ON TO THE OTHER, THE MATERIAL THAT GAINS ELECTRONS BECOMES NEGARIVELY CHARGED, THE MATERIAL THAT LOSES ELECTRONS IS LEFT WITH AN EQUAL POSITIVE CHARGE
Give an example of where friction happens
For example RUBBING A PLASTIC ROD (COMB) ON SOME MATERIAL WILL CAUSE A TRANSFER OF ELECTRONS, PLACE THE CHARGED ROD ABOVE BITS OF PAPER AND THE PAPER WILL GET ATTRACTED TO THE ROD BECAUSE THE OPPISETLEY CHARGED PARTICLES ARE ATTRACTED TO THE ROD
What does a charged object create around itself
A charged object creates an ELECTRICSL FIELD around itself
Where is an electric field strongest and the weakest
The electric field is strongest CLOSE TO THE CHARGED OBJECT, THE FURTHER AWAY FROM THE CHARGED OBJECT IS WHERE THE FIELD IS WEAKER
What happens when a second charged object is placed into the electric field
When a second charged object is placed in the field IT EXPERIENCES A FORCE, the force gets stronger as the distance between the objects decreases
What is the electric field
REGION AROUND A CHARGED PARTICLE WITHIN WHICH A FORCE WOULD BE EXERTED ON ANOTHER CHARGED PARTICLE
What happens when the electric field strength of a charged object is greater than the dielectic field strength
When the electric field strength of a charged object is greater than the dielectic field strength A SPARK CAN OCCUR. This is because when the dielectic field strength is exceeded there is an increase in free electrons in the air allowing the air to conduct electric and a spark is produced
Define dielectic field strength
THE MAXIMUM ELECTRIC FIELD STRENGTH, usually air, CAN HAVE WITHOUT BREAKING DOWN
What are lines of force
IMAGINARY LINE WHICH REPRESENTS THE STRENGTH AND DIRECTION OF A MAGNETIC, GRAVITATIONAL OR ELECTRIC FIELD
