P10 - P11 Flashcards
Difference between series circuit and parallel circuit
In a series circuit there’s only one path for the current to flow , in parallel there’s more than one path for the current to flow .
Same current flows through all components in a series circuit . In parallel current is determined by the split of current flow
In a a series the voltage is the sum of the voltage of the smaller components . voltage is the same in a parallel circuit
Describe a Voltmeter and Ammeter
Voltmeter used to measure voltage and connected in parallel
Ammeter used to measure current and connected in series
How can we describe a volt ?
1 joule per coulomb
Formula for energy transferred ( electrical energy )
Energy transferred = Charge x voltage
E = Q x V
Formula for charge
Charge = Current x Time
Q = I x T
What happens to current at a junction ?
Current is conserved at a junction in a circuit
What is the effect of a Resistor to the current - variable resistor
Inversely proportional to each other
If we increase the current the resistance decreases
If we increase the resistance the current deceases
What is he formula for voltage ( ohms law )
Voltage = Current x Resistance V = I x R
Explain what will happen with 2 resistors in a parallel and series
Series : The resistance will add up
Parallel : The resistance will decrease because current increases
How does the resistance of an LDR change with light intensity ?
In the dark , the resistance is very high so no current can flow through it
In the bright light , resistance will be low so current will be higher
How does a resistance of a thermistor change with temperature ?
At low temperatures , the resistance is high so little current can flow
At high temperatures , the resistance is low so more current can flow
What happens when there is an electric current in a resistor - why does this happen
There will be an energy transfer that heats the resistor
this is because of the collusion between electrons and ions
How to reduce unwanted energy transfer in a circuit
Use longer and thicker wires
Advantages and disadvantages of heat effect in electric current
Reduces lifetime of components in circuit
Cause a fire if too hot
Used in heaters , irons and water heaters
Fuse depends upon detecting heat
Formula for energy transferred
4 components
Energy = Current x Voltage x Time E = I x V x t
What is power and what is the unit
Power is the amount of energy transferred per second
measured in watts (W)
What are the 3 equations for power
Power = energy transferred / time
Power = Current squared x resistance
Power = current x potential difference
Factors affecting power transfer in a circuit
Potential difference and current
Difference between A.c and D.c electricity
Which one does the UK use - watts and Hz
A.c : Direction of current switches at regular intervals
D.c : Direction of current in 1 direction
Cells and batteries supply direct current
UK uses a.c At frequency of 50Hz and 230V
What is the function of an earth wire or circuit breaker
This is a safety precaution
earth wire connected to ground to earth
Circuit breaker breaks circuit if there’s a problem
What happens if the live wire and the earth wire touch
there would be an electric shock or a fire because there is a 230v difference between them
Relationship between power rating and change in stored energy
Higher the power rating , quicker the change in stored energy
How can an insulator be charged by friction ?
When 2 insulating materials rub against each other , they will become charged . Electrons will move from 1 insulator to the other so 1 will become positively charged and 1 will become negatively charged
Explain lightning and shocks in terms of the electron transfer
Shocks - Someone may become charged for example rubbing socks against a carpet , when this person comes into contact with a normal person thee electrons will go from the charged person to the normal person
Lightening - Clouds move over each other , this causes them to become charged because electrons are transferred between them . The ground is neutral , so the negative charges in the cloud jump to meet the positive charges on the ground , this creates a giant spark
How does earthing work ?
Earthing is removing excess charge by moving electrons
What are some uses of electrostatic charge
Spraying pesticides - Al the droplets are given the same charge so when they are sprayed out they go away from each other because same charges repel .
What are the dangers of filling up a car with fuel
there could be a build up of charge in the pipe because of the fuel rubbing against the pipe , this could cause a spark and cause an explosion
What is an electrical field
Region were charges experience a force
What is the value of a mA
1/1000 of an amp
