P2.3 Flashcards
What does static mean?
Still
What happens if a plastic is rubbed by a dry cloth?
~ The rod and cloth can become electrically charged
~ The plastic has an equal number of protons and electrons, as does the cloth
~ When rubbed some electrons from one can be transferred to the other which imbalances the charge on both of them
What do opposite charges do?
Attract
What do like charges do?
Repel
What are some examples of static electricity?
~ Balloons being rubbed on something and sticking to a wall
~ Van der graaf generator
~ Trampoline carpets
What charge does a gain of electrons give?
Negative charge
What charge does a loss of electrons give?
Positive charge
What does a voltmeter measure?
Voltage / potential difference
What does an ammeter measure?
Current (amps)
What does a fixed resistor do?
Lower the current, measured in ohms
What is a thermistor?
A heat sensor, used in thermostats
What are light dependent resistors used for?
Switching on circuits depending on whether there is light (like streetlights)
What can light emitting diodes be used for?
Making efficient lighting which only uses a little electricity but produces lots of light
What is electric current?
The flow of charge, measured with an ammeter
What is the measure of the large amount of electrons in an electric current?
1 coulomb
What is current a measure of?
The flow of coulombs per second
What does the letter I stand for?
Current (amps)
What does the letter Q stand for?
Charge (coulombs)
What is another word for potential difference?
Voltage
What is potential difference?
Energy transferred per coulomb of charge
What does work done mean?
Energy transferred
What is the units of potential difference?
Volts
What is work done/energy transferred measured in?
Joules
As the current increases what else increases?
Potential difference
Current is directly proportional to what?
The potential difference
In series circuits, the total resistance is the sum of…
All the individual resistors or components
In series circuits, the total potential difference of the cells is the sum of…
The individual cells
In a series circuit the potential difference is shared between…
The components
In series circuits, the current is…
The same throughout and through each component
In parallel circuits, the potential difference across each component is…
The same
In parallel circuits, the current is different…
In different branches of the circuit
In parallel circuits, the total current through the whole circuit is the sum of…
The current through the separate components
The higher the resistance…
The lower the current
The higher the temperature…
The lower the resistance, so more current can flow
A diode makes the current flow…
In only one direction
Why does the current decrease when a conductor is heated?
~ Heat causes the free atoms/ions to vibrate more
~ Electrons collide more frequently which reduces the current
What do electrically charged objects do when they’re brought together?
Exert a force on each other
What is current a flow of?
Charge
How can the resistance of a component be found?
By measuring the current through the components and the potential difference across the components
What is the measure of resistance?
Ohms
Why is the an increasing use of LEDs for lighting?
They use a much smaller current than other forms of lighting
As the resistance of a light dependent resistor decreases…
The light intensity increases
As the temperature of a thermistor decreases…
The temperature increases
What are uses of LDRs?
~ Automatic lights
~ Camera shutter
~ Fridge lights
What are uses of thermistors?
Heating systems
What are uses of LEDs?
Efficient lamps
