Electricity Flashcards
Define Electrical Current:
-Measure of the amount of charge that
goes past a point in the circuit in one second.
- The flow of charge
Define and Electrical Circuit?
A closed loop.
- must have an energy source
- A conducting pathway
-Something to put the energy into.
What is the Symbol, Units and measurement method for Electrical Current?
Symbol = I
Measured by an Ammeter
Units = ampere
Name some features of an ammeter:
- Low resistance to allow charge to flow through unmodified.
- Positive side must be connected to the nearest positive terminal of a battery.
Which way round does the Electrical Current Flow?
-Electrons leave the negative terminal of a power supply because they are repelled by the negative terminal
-However, we show the current as flowing from the positive terminal to the negative terminal!
Define Voltage:
Voltage is the amount of energy used up by a charge as it moves through a load/resistor.
- called potential difference or
voltage.
What is the Symbol, Units and measurement method for Voltage?
Symbol = V
Measured by a Voltmeter
Units = Volts
Name some features of a voltmeter:
-Used to measure the voltage/potential difference
between two points in an electric circuit.
-Connected in parallel
-Compare energy electrons have before and after they pass
through a component.
-Voltmeters have a very high resistance (So no charge can pass through them)
Define Resistance:
-A measure of how difficult it is
for a charged particle to move through it.
What is the Symbol, Units and measurement method for Resistance?
Symbol = R
Measured by Ohms Law
Units = Ohms (Ω)
Compare a Conductor vs and Insulator
Conductors allow electricity to flow through whilst Insulators do not allow electricity to flow through easily.
Identify features of a Series circuit:
- 1 continuous circuit
- If one thing breaks they all break
- Electrons have to pass through every component to loop back around again.
- e.g. christmas lights.
Identify features of a parallel circuit:
- more than one path for current to pass through.
- if one part breaks the current will still continue to flow around component
- e.g. household lights.
Conditions of drawing a circuit:
- Straight lines/ruler/pencil/eraser
- Power source goes on top
- No components on corners
Compare Voltage vs Current in Series and Parallel Circuits.
Series Circuits:
- Current is the Same everywhere
- Voltage splits amongst components.
E.g total Voltage = 6 and there are 3 lightbulbs each lightbulb will have 3 volts.
Parallel Circuits
- Current Splits amongst branches
- Voltage is constant everywhere.
E.g. total Current = 12 - 4 currents applied to each branch.
Describe Ohms Laws Triangle:
ㅤㅤV
I R
What does Ohms Law show:
The relationship between voltage drop across an ohmic resistor and the current flowing through it.
As the resistance of in a circuit increases the flow of electrons ______ and so does the current.
Decreases.
As the voltage in a circuit increases, the electrons have more energy and flow faster, and so the current ____
Increases.
What is an ohmic resistor?
An ohmic resistor is a resistor that has a constant resistance.
Explain the process of generation of electricity in a coal fired power station:
- Coal is mined and transported to the factories
- Coal is burned in a furnace
- Water is turned into steam due to this heat.
- Steam turns a turbine
- The steam then travels into cooling towers where it switches back to water to be re used.
- The turbine that is being spun turn a MAGNET wrapped in a COIL inside a GENERATOR
-The electrons from the wire begin to move creating a current. - The voltage gets stepped up by a transformer.
Why does the turbine turn?
High pressure steam from the heated water forces this movement.
What are step up transformers and step down transformers.
- Step up increase the voltage (good for travelling electricity quickly)
- Step down decrease the voltage so it is safe to stick into homes. (won’t blow a fuse.)
List one disadvantage and one advantage of coal powered plants.
Disadvantage: Maximum 50% efficiency.
Advantages: Coal can safely be transported.
When a wire is moved in a magnetic field, a voltage is induced causing a _________ to flow.
Current.
The same thing happens when a magnet rotates inside a ________. This is how ________ is created.
Coil.
Electricity.
Because the magnet is rotating, the current changes __________. We call this _________ current.
Direction.
Alternating.
We can increase the current by using __________ coils, a ________
magnet and faster ___________.
More.
Stronger.
Motion.
What is the equation for calculating the cost of electricity:
Total cost = Energy Transferred x Cost per unit.
Homer reads his electric meter and he has used 2034 units (kWh) since his last bill. He notices that he gets charged 15.3c per unit. What is his
total bill?
Total cost = 2034 x 15.3 = 31120.2c
= $311.20
How do you find the kWh (amount of energy used)? (What is the equation)
Energy = power x time
What does the energy, power, time triangle look like?
E
P T
Time is measured in?
Seconds.
Energy is measured in?
Joules.
Power is measured in?
Watts
How do you find the power equation?
P = e
-
t
What is the equation for energy efficiency
Energy efficiency = Useful Energy
———————
Total Energy
What are some factors that mean not all energy is efficient:
- Heat
- Light
- Sound
Energies
