Electricity Part 2 Flashcards
The resistance of a light dependant resistor decreases…
As light intensity increases
The resistance of a thermistor decreases…
As the temperature increases
What is the forward resistance for a diode like?
Low resistance so reverse resistance is high so there is negligible current in the reverse direction
What happened to the resistance of a LDR as light intensity increases?
Resistance of the LDR decreases at light intensity increases
What happens to the resistance of a thermistor as the temperature increases?
The resistance of the thermistor decreases as the temperature increases
What is the current through each component for a component connected in series?
The current through each component is the same for components connected in series
How can you calculate the total potential difference of components in series?
Adding the potential differences of each component gives the total PD
What is the total resistance of components connected in series?
The sum of the resistance of each component
What is the total current of component connected in parallel?
The sum of the currents through the separate components
What is the potential difference of each component in parallel?
The potential difference across each component is the same
For components connected in parallel the bigger the resistance ……………
The smaller the current
How can you calculate the current through a resistor in parallel?
Using the equation I= V/R
What is direct current?
Current that travels in one direction only
What is alternating current?
Current that repeatedly reverses
What is the peak voltage of an alternating potential difference?
The maximum voltage measured from zero volts
What Dee’s the live wire alternate between?
Alternates between positive and negative every cycle
What voltage is the neutral wire at?
Zero volts
In the uk what does the voltage alternate between?
325 and -325V
What is 325 and -325 in alternating current equal to in direct current?
230 in direct voltage
How can you measure the frequency of an a.c supply?
Measure the time period of the waves and then use the formula frequency = 1/time taken for one cycle
In the uk what is the mains supply frequency?
50Hz
What are sockets and plugs made of? And why?
They are made of stiff plastic that enclose the electrical connections
Plastic is used as it is a good electrical insulator
An appliance with a plastic case is said to be …………. …………….
Doug,y insulated
What do mains cables consist of?
2 or 3 insulated copper wires surrounded by an outer layer of flexible plastic material
What colour is the live wire?
Brown
What colour is the neutral wire?
Blue
What colour is the earth wire?
Green and yellow
Which pin is the earth wire connected to?
The longest pin
What is the earth wire used for?
It is used to earth the metal case of a mains appliance
What is a fuse?
A thin wire that heats up and melts cutting of the current if the current is too large
How is a fuse fitted?
It is fitted in series with the live wire so if the fuse blows ipthe current from the live wither is cut off
What is a circuit breaker?
An electromagnetic switch that opens and cuts off the current in the live wire if too much current passes through the circuit breaker
Why is a circuit breaker better than a fuse?
It works faster
Can be reset quickly
What does RCCB stand for?
Residual current circuit breaker
What does a RCCB do?
Cuts off the current in the live wire if it is different from the current in the neutral wire
What is the benefit of RCCB?
It is more sensitive than both a fuse and a circuit breaker
Why does a mains appliance with a plastic case not need to be earthed?
Plastic is an insulator and cannot become live
Why should appliances with metal cases be earthed?
So that if a fault occurs the metal case is safe to touch
What is power?
The energy transferred to an appliance each second
When an electrical charge through a resistor ……….. ………… To the resistor makes it …..
Energy
Transferred
Hot
When a ……. Flows round a circuit for a certain time the ……….. Energy supplies by the battery is ……….. To the electrical energy transferred to ….. Components in the circuit
Charge
Electrical
Equal
All
Why are electrical faults dangerous?
They can cause electric shocks and fires
What should you consider when choosing an appliance?
Power and efficiency
Filament bulbs and halogen bulbs are much ……. Efficient than ….. Energy bulbs
Less
Low
You should tough a mains appliance or plug or wicket with ….. …… And should never touch a bare wire or terminal at a potential of more than ……
Wet hands
30V
