7E Electromagnets Flashcards
What is a circuit symbol?
A diagram used to represent a component
What represents a wire in a circuit diagram?
A straight line
What is a cell?
The power source in a circuit ( what we usually call a battery)
What is a battery?
Two or more cells
Why do we use circuit diagrams?
To make it easier to see what is connected to what in a circuit
What should you use to draw a circuit diagram?
Use a pencil and ruler, use correct symbols
What should you draw first when drawing a circuit diagram?
The symbols
What is a lamp?
Another name for a bulb
What has to happen for a circuit to work?
All components must be connected
How does a switch work?
It causes two pieces of metal to touch and complete the circuit
What makes a lamp light up?
Current passing through it
What does the battery do in a circuit?
It makes the current flow around the circuit
Why does a higher voltage affect the brightness of a bulb?
It creates a higher current, so the bulb is brighter
What is current?
Flow of electric charge
Why does charge all start moving at the same time?
The charge is evenly spread through the wires
What must a circuit always contain?
A power supply, no gaps
What do you use to measure the potential difference of a cell or a battery?
Using a voltmeter
What is the potential difference of the mains electricity?
230V
What happens if there is an increase in the voltage?
A bigger push and a bigger current
What does potential difference actually mean?
The difference in energy between two different points in the circuit
How do you increase the potential difference in a circuit?
Increasing the power supply
How does the voltmeter need to be connected in a circuit?
In a parallel circuit
What is the potential difference in a circuit with 3 1.5V cells?
4.5V
What might happen to a lamp when you add more cells?
It will get brighter
What is an electrical conductor?
A material that allows electricity to pass through easily
Give 2 examples of conductors.
Any names metal, graphite
What is an electrical insulator?
A material that does not allows electricity to pass through easily
Give 2 examples of insulators.
Plastic, rubber, glass
What is resistance?
The opposition to the movement of electrical charge
WHat are the units that resistance are measured in?
Ohms (Ω)
What is the relationship between current and resistance?
Higher current = lower resistance
Name 2 factors that can affect resistance?
Material, length of wire, thickness of wire, temperature
Which type of circuit will have only one pathways for current to flow?
Series
Describe the structure a series circuit.
Components connected end to end in a loop.
Describe the structure of a parallel circuit.
Components connected side by side in different loops.
Explain why the voltage and current might be different in the two types of circuit
In series there is only 1 pathway for the electricity to follow, in parallel there can be many.
What is the rule for p.d in a series circuit?
Potential difference is shared across each component.
How do you calculate resistance in a series circuit?
Add the resistance from each resistor.
What is the rule for p.d in a series circuit?
Potential difference is the same across each loop.
What is the rule for resistance in a parallel circuit?
the total resistance of the circuit is reduced as the current can follow multiple paths
What does current do?
Transfers energy in a circuit
What are the two types of current?
Alternating and direct
How are the two types of current different?
Direct only goes in one direction alternating continually reverses
What are electrons?
Negative charged particles
What is the difference between a series and parallel circuit?
Series is one loop parallel is many
What is a problem with series circuits?
One component goes and the current cannot flow
What is an advantage of series circuits?
Less wires
Why are homes wired with parallel circuits?
If one bulb goes the others keep working
What is resistance?
A measure of the opposition of flow of electricity
What does the symbol represent?
Ohms
State the calculation for resistance
Resistance = potential difference/ current
Rearrange the calculation to find current:
Current = potential difference/ resistance
What is Ohms law?
When resistance stays the same potential difference and and current are directly proportional
How do you connect a voltmeter in a circuit?
In parallel
How do you connect an ammeter in a circuit?
In series
What does the term directly proportional mean?
As one variable increases the other increases by the same amount
Does electrical current flow more easily in air or water?
In water
Why is it dangerous to play around overhead wires?
The electricity could pass through your body if you come into contact with the wires
What can an electrical shock do to your body?
It can affect your muscles and nerves, paralyse you or stop your heart.
What colour is the earth wire in a plug?
Green and yellow striped
What is the function of the live wire in the plug?
It carries the electrical current
What is the function of the neutral wire in a plug?
It completes the circuit
How does a fuse work?
It contains a thin wire that melts if current is too high
Why are the outer casings of electrical appliances covered in plastic?
It is an insulator (electricity will not pass through)
What is a theory?
Explanation to explain an phenomena
What is a model?
Helps visualise things that cannot be seen
Why do we use models?
Help understand ideas
When should we use models?
After the scientific explanation
What is an electric field?
Area around a charged object where a force can be felt
What causes an electric field?
A charged object
What 2 things can happen in an electric field?
Objects can attract or repel
Why can the 2 things happen in an electric field?
Like charges will push away from each other, opposite charges will pull towards each other
What direction does an electric field occur in?
From positive to negative charges
What might happen as you move away from the charge?
Effect is less, force gets weaker
What does the comb in a Van de Graaff generator do?
Is given a positive voltage to attract electrons from the belt
Why do hairs stick out in every direction if you touch the VdG generator?
They repel the scalp and each other
