P3 - Electricity Flashcards
What charges do protons and electrons have?
Protons have positive charge
Electrons have negative charge
What are the charges of the three subatomic particles ?
Protons - +1 charge = mass of 1
Neutrons - 0 charge = mass of 1
Electrons - -1 charge = mass of 0.0005
Why is an atom neutral?
Same number of protons and electrons
Positives and negatives cancel our
How do we generate static charge?
Electrons are moving
If two insulators are rubbed, electrons get transferred from one insulator to the other.
Therefore one insulator is going to have more electrons than protons - negatively charged
Vice versa
How can we discharge an object?
Connect the object to piece of metal meaning charges can flow therefore object becomes discharged
Spark - flow of current through the air.
What is current?
The rate of flow of charged particles which are the electrons.
Cell , battery or power supply is need to make current flow as well as a complete circuit
Explain the current in a single closed loop?
Current is going to be the same anywhere
What is the formula for charge flow?
Charge flow (C) = current (A) * time (S)
What is potential difference?
Required for the current to flow in a circuit.
Caused by the separation of charges inside the cell or battery
Which terminal had a higher electrical potential?
Positive charge has a higher electrical potential than the negative charge
How is potential difference measured?
Using a voltmeter
Volts
Which lines is the positive and negative terminal
Positive terminal - longer lines
Negative terminal - shorter lines
What happens when we apply potential difference between ends of a wire?
Electrical fuels is being set up
What is the formula for energy transferred?
Energy transferred (J) = potential difference (V) * charge (C)
Explain the series circuit?
- current is the same everywhere
- work out the current using ammeter
If we wanted to know pd what do you do?
Place a voltmeter in parallel circuit
Explain series circuit in terms of reading volt meters?
The reading on all voltmeters across the components is equal to the reading across the battery.
Explain parallel circuit in terms of current?
The current in all the loops adds up to the current near the battery.
The pd across each component is the same as across our battery
How can you troubleshoot it your light doesn’t light up?
- connect bulb to the battery
- if doesn’t work try another battery
- if doesn’t work try another bulb
- replace single wire at a time until all wires are checked
What does current depend on?
- Potential difference And resistance in the circuit
Resistance is measure in ohms.
Current is dependent variable , so we can only change it by changing pd or resistance.
What is ohms law?
Current is proportional to the potential difference if the temperature does not change
Why does the resistance of some components change?
Metal is made up of positively charged ions arranged in a regular pattern. The outer shells has lost some electrons which have become delocalised.
Because they’re delocalised, free to move.
When delocalised electrons collide with metal ions , resistance is produced.
Explain resistance in wires.
Thinner wires or longer wires = greater resistance because greater chance of electrons colliding with the positive metal ions.
Thicker wire = lower resistance
What is a variable resistor?
Change the resistance … changing amount of current that then can flow through the circuit.
E.g. dim switches. Twisting means changing the number of coils of the wire that the current is actually flowing through therefore changing resistance.
What is a characteristic graph
Current plotted against potential difference.
What is a linear circuit element
Component that has a resistance that does not change. E.g. fixed resistor
Identify by straight line
What is a non linear circuit element ?
Component that has a resistance that does change.
E.g. lamp
Not a straight line so resistance is changing.
As the electrons collide with the metal ions in the wire, the ions vibrate more. This makes the wire get hotter.
What is a diode and explain the circuit graph?
Divides only let current flow one way,
Only flow one way so no negative.
