electricity Flashcards
What two factors does the current in the circuit depend on?
potential difference (V)
Resistance (R)
what is an Ohmic conductor state? The condition required?
A conductor for which current and potential difference are directly proportional
Resistance remains constant as current changes
temperature Must be constant
List four components for which resistance is not constant as current changes
lamps, diodes ,thermistor, light dependent resistors 
What happens to the resistance of a filament lamp as the temperature increases and why?
resistance increases
Irons and metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow
what is the different about current flow through a diode
The current only flows in One Direction
resistance is very high in other direction, preventing in current flow 
State what happens to the resistance of a thermistor as temperature increases
The thermistor resistance decreases
give two examples of when a thermistor may be used
in thermostat to turn the heater on below a certain temperature
In a freezer to turn on a cooler when the temperature becomes too high
State what happens to the resistor of LDR as light intensity decreases
The LDR resistance increases
Give an application for an LDR
Street lights often use ldr
when light levels become too low, the light gains sufficient current turn on 
what are the two ways that are component can be connected in a circuit?
Series(same loop)
Parallel (adjacent loop)
how does the potential difference across two components vary when connected in series and parallel? 
series: total potential difference is shared between each component
Parallel : potential difference across each component is the same
If two resistors are connected in parallel, what can be said about their combined total resistance?
Their total resistance is less than the smallest of the two individual resistances
If two resistors are connected in series, what can be said about their total resistance?
The total combine resistance is equal to the sum of the two individual resistances
Describe the current in a series circuit
In a series circuit, the current is the same at all positions since the charge only has one path to flow through
describe the current in a parallel circuit
In a parallel circuit, the current is shared between the different branches. When the charge reaches a junction it splits.
how should you connect ammeter in circuit to measure current?
Amita should be connected in series with the component that they are measuring current through
how should you connect voltmeter in circuit to measure potential difference?
voltmetre should be connected in a parallel to the component that they are measuring the potential difference of 
Why is it advantageous to connect lamps in parallel?
if one lamp blows, the rest will be unaffected and can still receive current
Is mains electricity an AC supply or a DC supply? What did each of these stand for?
mains electricity is an AC supply
AC: alternative current
DC: Direct current
Define alternating current and direct current
alternative current: current that continuous changes direction at a specific frequency
Direct current: One Direction current flow
What is the frequency and voltage of the UK mains electricity supply?
frequency:50 Hz
Voltage: 230V
How many wires are usually in the cables connecting electrical appliances to the mains? Name these wires.
- Live wire.
- Neutral wire.
- Earth wire.
State the insulation colour used on the earth wire
Green and yellow stripes
State the insulation colour used on the live wire
Brown
State the insulation colour used on the earth wire
Blue
explain when the Earth wide does and doesn’t carry a current
In the normal circumstances, no current flows through the earth wire
 if a fault occurs in the appliance(such as a surge or the casing becoming live) current will flow to the ground
What potential is the neutral wire at?
0 volts
State the potential difference between the live and earth wire
230 v
What is the purpose of a neutral wire?
To complete the circuit by connecting the appliance back to the main supply
The metal appliances, where is the earth wire connected to and why?
Earth wire connected to the metal casing of the appliance
if live Wyatt becomes loose and touches the case in the current flow through the Earth by preventing electrocution
what two main factors does the amount of energy transferred by appliance depend on
How long the appliances being used for?
The power of the appliance
describe the energy transfer in a battery powered torch
battery converts chemical energy into electrical energy
bulb convert electrical energy into light as well as waste energy in the form of heating
Describe the energy transfers in a battery powered motor
battery converts chemical energy into electrical energy
Motor converts electrical energy into kinetic energy as well as waste energy in the form of heating due to friction
what three things determine the power of a circuit device?
The potential difference across the circuit
The current through the circuit
The amount of energy transferred in a given time
What is the purpose of the national grid?
To link power stations to consumers so that they have access to source of electricity
what are two types of transformers used in the national grid?
Step up transformer
Step down transformer
Where are step up transformers found in the National Grid and what do they do?
step up transformers are used when connecting power stations to transmission cables
They increase the potential differences
why do transmission lines transfer electricity at high potential?
At high potential result in a low current
The lower the current the less energy that is wasted as heat
Therefore, it is more efficient
Why does the potential need to be creased between transmission lines and houses?
lower potentials are safer if it’s domestic use and reduces the likelihood of severe electrocution
appliances are designed for 230 V 
what can happen when insulating a material of rubbed together?
They can become electrically charged
why can insulators become electrically charged when rub together?
 electrons are rubbed from one material onto the other
The material gaining electrons become negatively charge
The material losing electron becomes equally positively charged
What happens when two electrically charge objects are brought close together?
They exert force on each other
what happens when two identical charge objects are put close together?
The repulsive force on each other and repel
What happens when two opposite charge objects are brought close together?
they exert an attractive force on each other and attract
Give an example of a noncontact force
they repulsive or attract force acting between two electrically charge objects
What is an electric field?
Region in which a charge objects will experience a noncontact electrical force
Where can electric fields be found?
Surrounding any charged object
describe the electric field around a charge particle
Strongest closest to the object
Decreases in strength as you move away from the object
What happens to the force between two charge objects when they moved closer together?
The force between them becomes stronger as the separation reduces
In situations where sparks are unwanted what precaution must be taken to prevent the buildup of static charge
Any surfaces that are rubbing against each of us should be earth to allow the charge to flow off the materials
