Physics revision Flashcards
1
Q
Formula for Q(charge)
A
I x t (current x time)
2
Q
How to calculate the end time if they don’t tell you (V^2)
A
V^2 = U^2 + 2as
3
Q
What are the units for Q (the charge)
A
C
4
Q
What are the units for I (the current)
A
A
5
Q
What are the units for F (the force)
A
N
6
Q
What are the units for E (the energy)
A
J
7
Q
What are the units for the V (the voltage)
A
V
8
Q
What are the types of energy transfers?
A
energy transfers: mechanically, electrically, by heating, by radiation (light and sound)
9
Q
What are the types of energy stores?
A
energy stores: chemical, kinetic, gravitational, elastic, thermal, magnetic, electrostatic, nuclear
10
Q
What are the units for power?
A
Watts(W)
11
Q
What are the units for work done
A
Joules(J)
12
Q
What’s the equation for average speed?
A
distance moved / time taken
13
Q
What’s the equation for acceleration?
A
change in velocity / time taken
14
Q
What’s the equation for final speed^2
A
final speed ^2 = (initial speed^2) + (2 x acceleration x distance moved) –> v^2 = u^2 +(2 x a x s)
15
Q
How to calculate weight?
A
Mass x gravitational field strength –> W = m x g
16
Q
What’s the equation for power in a circuit?
A
current x voltage
17
Q
What’s the equation for energy transferred?(if they give 3 values)
A
current x voltage x time
18
Q
What’s the equation for voltage
A
current x resistance
19
Q
What’s the equation for the charge
A
current x time
20
Q
What’s the equation for energy transferred?(if they give 2 values)
A
charge x voltage
21
Q
What’s the equation for efficiency?
A
useful energy output / total energy output x 100
22
Q
What’s the equation for work done?
A
force x distance moved
23
Q
What’s the equation for gravitational potential energy?
A
m x g x h
24
Q
What’s the equation for kinetic energy?
A
1/2 x mass x speed^2
25
What's the equation for power?
work done/ time taken
26
What's the equation for density?
mass / volume
27
What's the equation for pressure
force / area
28
What's the equation for pressure difference?
height x density x gravitational field strength
29
What is the pressure law?( lussacs law)
pressure / temperature = constant --> P1/T1 = P2/T2
30
What is Boyle's law?
pressure x volume = constant --> p1 x V1 = p2 x V2
31
What is the principle of conservation of energy?
Energy is never created or destroyed. It just transfers from one to another
32
describe how thermal energy transfer may take place by conduction
Conduction is the transfer of thermal energy through a substance by the vibration of the atoms within the substance. Metals are good conductors because they have free electrons that can move easily through the metal, making the transfer of energy happen faster.
33
describe how thermal energy transfer may take place by convection
Convection occurs in a liquid or gas. These expand when heated because the particles move faster and take up more volume – the particles remain the same size but become further apart. The hot liquid or gas is less dense, so it rises into colder areas. The denser, colder liquid or gas falls into the warm areas. In this way, convection currents are set up which transfer heat from place to place.
34
describe how thermal energy transfer may take place by radiation
Thermal radiation is the transfer of energy by infrared (IR) waves. These travel very quickly in straight lines.
35
explain ways of reducing unwanted energy transfer, such as insulation
A good insulating material is a poor conductor that contains trapped air, e.g. foam, feathers, glass fibre. Being a poor conductor (non-metal) prevents heat transfer by conduction and the trapped air prevents convection currents.
36
What is work done equal to?
work done is equal to energy transferred
37
What is power described as?
describe power as the rate of transfer of energy or the rate of doing work
37
understand how the pressure at a point in a gas or liquid at rest acts equally in all directions
understand how the pressure at a point in a gas or liquid at rest acts equally in all directions
37
explain how molecules in a gas have random motion and that they exert a force and hence a pressure on the walls of a container
Gas laws:
- Gas molecules have rapid and random motion.
- When they hit the walls of the container, they exert a force.
38
why there is an absolute zero of temperature which is –273 °C
At absolute zero the particles have no thermal energy or kinetic energy, so they cannot exert a force
39
How to find the C from kelvin
-273
40
How to find kelvin from C
+273
41
know that the Kelvin temperature of a gas is proportional to the average kinetic energy of its molecules
know that the Kelvin temperature of a gas is proportional to the average kinetic energy of its molecules
42
explain, for a fixed amount of gas, the qualitative relationship between:
* pressure and volume at constant temperature
* pressure and Kelvin temperature at constant volume.
As you heat the gas, the kinetic energy of the particles increases, and thus so does their average speed.
This means more collisions per second with the walls, and they exert a larger force on the wall.
This causes in the total pressure being exerted by the particles to rise.
If temperature is constant, the average speed of the particles is constant.
If the same number of particles is placed in a container of smaller volume they will hit the walls of the container more often.
More collisions per second means that the particles are exerting a larger force on the wall over the same time, so average force exerted on the walls has increased.
43
understand how the use of insulation, double insulation, earthing, fuses and circuit breakers protects the device or user in a range of domestic appliances
Fuses Stop the flow of current by melting if the current is too high. So protecting sensitive components and people because if the components function at too higher temperature it can cause a fire.
Circuit breakers again break the circuit if current is too high.
Insulation and double insulation prevent people from touching exposed wires and getting shocks.
Earthing provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.
44
understand why a current in a resistor results in the electirical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts
Resistance causes transfer of electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens, for example electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced.
45
know the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery
AC is constantly changing magnitude and direction. AC is how mains electricity is produced from turbines.
DC is constant. And is produced from a battery and used in some sensitive components like in computing.
46
describe how current varies with voltage in wires, resistors, metal filament lamps and
diodes, and how to investigate this experimentally
Check book
47
describe the qualitative effect of changing resistance on the current in a circuit
Since V = IR, as you increase the resistance in a circuit, the current will decrease.
48
describe the qualitative variation of resistance of light-dependent resistors (LDRs) with illumination and thermistors with temperature
LDR
As illumination increases, resistance decreases
Thermistor
As temperature increases, resistance decreases.
49
know that lamps and LEDs can be used to indicate the presence of a current in a circuit
know that lamps and LEDs can be used to indicate the presence of a current in a circuit
50
know that current is the rate of flow of charge
know that current is the rate of flow of charge
51
know that electric current in solid metallic conductors is a flow of negatively charged electrons
know that electric current in solid metallic conductors is a flow of negatively charged electrons
52
know that the voltage across two components connected in parallel is the same
know that the voltage across two components connected in parallel is the same
53
calculate the currents, voltages and resistances of two resistive components connected in a series circuit
VT = V1 + V2
IT = I1 = I2
RT = R1 + R2
54
know that:
* voltage is the energy transferred per unit charge passed
* the volt is a joule per coulomb.
know that:
* voltage is the energy transferred per unit charge passed
* the volt is a joule per coulomb.
55
know that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance
know that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance
56
know that the initial linear region of a force-extension graph is associated with Hooke’s law
Hooke’s law is that extension is directly proportional to force applied. This is shown by the straight line on the force-extension graph. Hooke’s law is obeyed as long as the line is straight.
57
describe the effects of forces between bodies such as changes in speed, shape or direction
Changes in speed: forces can cause bodies to speed up or slow down. Changes in direction: forces can cause bodies to change their direction of travel.
Changes in shape: forces can cause bodies to stretch, compress, or deform.
58
identify different types of force such as gravitational or electrostatic
Gravitational (or weight) - the force between any two objects with mass (like the Earth and the Moon)
Electrostatic - the force between any two objects with charge (like a proton and an electron)
Thrust - the force pushing a vehicle (like the push from rocket engines on the shuttle)
Upthrust - the upward force on any object in a fluid (like a boat on the surface of a river)
Air resistance (or drag) - the force of friction between objects falling through the air (like a skydiver in freefall)
Compression - forces that squeeze an object (like squeezing a spring)
Tension - forces that stretch an object (like two teams in a tug-of-war)
Reaction force - the force between any two objects in contact (like the upwards force from a table on a book)
59
understand how vector quantities differ from scalar quantities
Vector quantities have two characteristics, a magnitude and a direction.
Scalar quantities have only a magnitude.
60
understand that force is a vector quantity
A force has both magnitude and direction, therefore: Force is a vector quantity; its units are newtons, N.
