P2 Physics Flashcards
Define current.
The rate of flow of charge.
What does LDR and LED stand for?
LDR = Light dependant resistor
LED = Light emitting diode
What is an electrical conductor?
A material that allows an electrical current to pass through it.
What is static electricity?
When charge builds up on an object and then stays ‘static’ as there is nowhere for the charge to flow away.
What is an electrical insulator?
A material that does not allow an electrical current to pass through it easily.
What are the two things needed in a circuit that are needed to allow current to flow and for the circuit to work?
A power source and a complete circuit.
What is charge?
A property of matter that can be positive or negative, it’s measured in coulombs (c). When charge moves, a current is created.
Where does conventional current flow from?
Positive to negative.
What is resistance?
Resistance is anything that will stop or slow down a current, it’s measured in ohms.
What happens to the voltage and the current in a parallel circuit?
The voltage stays the same across each branch and the current splits down each branch.
Take a few minutes to practice circuit symbols in the book.
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What happens to the voltage and the current in a series circuit?
Voltage is shared between the components and current is the same at any point.
What are some of the applications of thermistors?
Household heating systems, Car engines
What are some of the applications of LDR’s?
Automatic night lights and street lamps, some burglar alarms.
Have a few minutes looking in the book and memorizing the differences between a ceramic resistor, a diode, and a filament lamp.
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Describe what happens to the filament lamp when current is flowing through it?
As current increases, the atoms in the filament lamp begin to vibrate and this increases the temperature. This increases the resistance too which means there is less current for the same increase in potential difference.
Describe what happens to a diode when there is current flowing through it?
A diode only allows current to flow in one direction. No current will flow if it’s pushed the wrong way as the diode’s resistance remains very large. When forward, the diode’s resistance is very large at low potential differences but when potential difference is higher, the resistance quickly drops and the current begins to flow.
Describe what happens to a ceramic resistor when current flows through it?
Potential difference is directly proportional to the current, this relationship is called ohm’s law and is true as the resistance of the resistor is fixed and does not change.
What is meant by an electric power?
Can also be defined as the rate of transfer of energy.
If there is a higher power, what happens to the current?
A higher power means a greater current flows for a given period.
What is meant by a direct current?
When the current only flows in one direction.
Electricity provided by a battery is known as what?
D.C. - Direct current, a typical battery has a voltage of 1.5 V.
What is meant by an alternating current?
When the current is constantly changing direction.
What is the standard UK mains in terms of potential difference and direction of current flow?
Mains electricity is A.C. (alternating current) with a voltage of 230 V and a frequency of 50 Hz