Physics Flashcards
What is terminal velocity
when the weight of the object falling and the air resistance is the same, therefore leaving us with no resultant force
What is the SI unit of density
kg/m³
What does density equal to
Density = mass/volume
what is hooke’s law
a law stating that the strain in a solid is proportional to the applied stress within the elastic limit of that solid.
What is the weight of a body of mass 1kg
the weight of a body of mass 1kg is 9.8N (often taken as 10N)
What is the weight of a body
The weight of a body is the force of gravity on it
Weight equation
weight equals mass X gravitational field strength
How to determine resultant force on a suspended weight
Amount of Newtons (on cable) x sine(angle the cable makes with horizon)
What does moment equal to
Force X distance
How long can an object stay upright
until the centre of mass is outside the base
the greater the distance from the hinge… (moment)
The less force required to move an object
What is work
Work is force x distance moved in direction of force
what are the two quantities to measure to calculate the useful work done when a load is lifted from the ground to a higher level
Weight and height
Why is the force required to lift a load higher when it is just leaving the floor
there is a force needed to get it started
What is the unit of work
Joules, the work done when 1 newton moves through 1 meter
What is the Kinetic energy equation
which is 0.5mv^2
Name three different emerge resources used to obtain energy directly from water
hydroelectric
tidal
wave
How does wave energy convert to electrical energy
Wave power converts the periodic up-and-down movement of the oceans waves into electricity by placing equipment on the surface of the oceans that captures the energy produced by the wave movement and converts this mechanical energy into electrical power.
what is gas pressure equal to
Atmospheric pressure + pressure due to liquid column
resistance equation
Voltage(V)/resistance(A)
How many Amps is one mA
1000
What measures current
Ammeter
what measures volts (pd)
Voltmeter
how to calculate current
Current = voltage/resistance
voltage equation
Current x resistance
how do variable resistors work
A variable resistor works by adjusting the path that current has to flow. … The dial you turn will move another piece of wire inside the resistor. The end result is that the electricity will travel through a certain length of the strip depending on where you turn the knob.
what are the two types of resistor setups
Parallel, series
How to calculate combined resistance in parallel
1/R1 = 1/R1 + 1/R2 etc… 1/R1 = 3/R2 R1/1 = R2/3
When is a current induced in the wire (u shaped magnet)
A current is induced in the wire when it is moved up or down between the magnet poles
What does the voltage increase with
the speed of motion of the magnet or coil
The number of turns on the coil
the strength of the magnet
What is Faraday’s law
The size of the induced p.d. is directly proportional to the rate at which the conductor cuts magnetic field lines
what is Lenz’s law
The direction of the induced current is such as to oppose the change causing it
Right hand rule
thuMb: Motion
First finger: Field
seCond finger: induced Curret
How does a simple a.c. generator (alternator) work
It consists of a rectangular coil between the poles of a C shaped magnet
The ends of the coil are joined to two split rings on the axle and against which carbon brushes press. When the coil is rotated it cuts the field lines and a voltage is induced in it
How does a simple d.c. generator (alternator) work
An a.c. generator becomes a direct current if the slip rings are replaced by a commutator like that in a d.c. motor
The brushes are arranged so that as the coil goes through the vertical, changeover of contact occurs from on half of the split ring of the communicator to the other. But it is when the coil goes through the vertical position that the voltage induced in the coil reverses, so one brush is always positive and the other negative
transformer equation
Secondary voltage/primary voltage = secondary turns/primary turns
How is voltage increased/decreased across transmission lines
Step up/ step down transformers
What is the purpose of the iron core
Magnetic linkage
List five devices that make use of electromagnetic induction
transformer, generator, dynamo, microphone, alternator
What is meant by electromagnetic induction
Magnetic field cut by conductor induces a current
how to increase the magnitude of the induced emf in this experiment
Move magnet faster, stronger magnet, more turns of solenoid
how to calculate mass of water
Mass = volume × density
How to calculate work
Work = Force × Distance
How to calculate density of liquid
divide mass by volume
what increases the sensitivity of a thermometer
A capillary tube with a very small diameter
define virtual image
an optical image formed from the apparent divergence of light rays from a point, as opposed to an image formed from their actual divergence.
How is a virtual image made
Virtual images form when light rays from the same location on an object reflect off a mirror and diverge or spread apart. Real images form when light rays from the same location on an object reflect off a mirror and converge or come together.
A student wants to demagnetise a steel bar. He switches on the circuit for a few seconds and then switches off. He finds that the steel bar is still magnetised.
How should he improve his method
Remove the steel bar from the coil whilst the circuit is switched on
REMINDER
Study logic gates and circuits, can’t do flash cards for it
A beam of electrons is passed through the magnetic field of a magnet, how must the magnet be positioned to deflect the beam in the direction shown
Have the magnet on its side, with S on the top and N on the bottom, when the electrons go through it will be redirected
