Unit 3 Flashcards
What is resistance?
How much of a component opposes the flow of current
As total resistance increases what happens to the current?
It decreases
What is resistance measured in?
Ohms
What kind of charge does an electron have?
Negative
What kind of charge does a proton have?
Positive
What do objects with the same charge do when placed close together?
Repel each other
What do objects with opposite charge do when paced close together?
Attract each other
Are electrons free to move in a conductor?
Yes
Are electrons free to move in insulators?
No
What happens when two insulators a rubbed together?
Become electrically charged - transfer electrons between them though friction
How are the comments linked in a series circuit?
In a loop
How would make an object positively/ negatively charged?
Electrons must be added/ removed
What is current?
The amount of charge flowing per second
What is current measured in?
Amperes (A)
What is one amp equal to?
One columb per second
What is an electric field?
The region around an electric charge
What do electrical field lines indicate?
The force exerted on a positive electric charge. Lines closer together - greater force exerted
What is voltage?
A measure of the energy given to the charges in a circuit
What is voltage measured in?
Volts (V)
What is potential difference?
Measure of the difference in energy across two points in a circuit
What does one volt equal?
One joule per coulomb
What is a voltage divider circuit?
Uses two or more resistors in series to provide a part of a supply voltage
Why are voltage divider circuits used?
To prevent a component getting damaged
In a voltage divider circuit is the current equal at all points?
Yes
When temperature is increased on a thermistor, what happens to the resistance?
It decreases
When light increases in a LDR, what happens to the resistance?
Decreases
What does a diode allow the current to do in a circuit?
Flow in one direction
What can a diode do to the power in a circuit?
Change it from AC to DC
What is a transistor?
A voltage controlled switch, responds to a change at the input
What are the two types of transistors?
Bi-polar transistor and MOSFET
What are capacitors?
Components that store charge and energy
What happens when a capacitor is connected to a power supply?
Capacitor charges and a potential difference is created across the capacitor
When resistance increases, what happens to the time taken for capacitor to charge?
Greater time to charge
Capacitors can be used in what type of circuits?
In timing circuits, eg-alarms
What is power?
How much energy is transferred per second
What is power measured in?
Watts (W)
How is power loss in transmission lines calculated?
P=I^2R
What does a step up transformer in power lines do?
Increases voltage across transmission lines
Wha does a step down transformer do in transmission lines?
Reduces voltage to a safe level
How is power loss reduced in transmission lines?
Voltage is increased meaning current decreases
What is a fuse?
A wire with a low melting point
If the current in a circuit is too high what happens to the fuse?
Heats up and melts
What is a ring circuit used for?
Used to connect a set of main sockets
What are some advantages of ring circuits?
Lower current in wires, thinner wires (less current), low cost, mains sockets can be easily added/removed
What is energy measured in?
Joules (J)
What is gravitational potential energy?
A object gains this energy when it is raised
What is kinetic energy?
An object gains this energy when it’s moving
Can energy be created or destroyed?
No energy is lost or transformed from one type to another
When a ball is dropped what kind of energy has it got?
Potential energy hen when dropped it is transformed into kinetic energy
During every energy transfer some energy is lost to the surroundings as what?
Heat energy
What does lost energy equal?
Initial energy - final energy
What is the efficiency of a device?
How much of the energy input is transformed into useful energy output
What is temperature?
A measure of how hot or cold an object is
To find the temperature in kelvin what do you do?
Tc + 273
When a substance is heated what happens to the atoms?
Atoms vibrate faster and kinetic energy of atoms increases
What is conduction?
Thermal energy is transferred by vibrating atoms
What is convection?
Thermal energy is transferred by movement of atoms within a substance (only happens in liquids and gases)
What is radiation?
Thermal energy is radiated as electromagnetic waves
What is specific heat capacity?
The amount of heat energy required to change the temperature of 1 kg of a substance by 1 degree
What is pressure?
The force per unit area
What is pressure measured in?
Pascals (Pa)
What is an example of high pressure?
Sharp knife through food
What is an example of low pressure?
Snow boots
In a kinetic model of gas does each particle have different values of kinetic energy?
Yes, they move at different velocities
What is Boyle’s Law?
Pressure is inversely proportional to a fixed mass of gas at a constant temperature
What is the equation for Boyle’s Law?
p1V1 = p2V2
What is the Pressure Law?
For a fixed mass of gas at a constant volume , pressure is directly proportional to temperature
What is the equation for Pressure Law?
p1/T1 = p2/T2
What is Charles’ Law?
As temperature increases, volume increases. For a fixed mass of gas at a constant pressure
What is the equation for Charles’ Law?
V1/T1 = V2/T2
What is the general gas equation?
p1V1/T1 = p2V2/T2
