Flashcards in Part 2 Deck (41)
what is current?
the rate of flow of charged particles
what are electrical conductors?
electrical conductors are materials that allow a current to pass through them. To do this they need to have 'free' electrons, because current is a flow of electrons. Metals have free electrons because of the way they are bonded (atoms and electrons within a lattice) this means they are good electrical conductors
what are the effects of forces on bodies and changes of speed?
when an object is stationary it has an equal force pushing down and up. The downward force being gravity and the upward force being the surface the object is on. When an object is accelerating it has the upwards and downwards forces but it also has the forwards and backwards forces (drag and friction). The forward force is larger than the backward force when an object is accelerating. When an object is at constant speed the forward and backward forces are equal, so the speed doesn't change speed
what are the effects of forces on bodies and changes in shape?
changes in shape affect momentum. Force= momentum/ time taken. An example of this is crumple zones in cars decrease the force on the passengers
how do forces affect bodies and changes of direction?
whichever direction the force is greatest in will be the direction the object travels in
what are the different forces?
- gravity- acting downwards
- upthrust- acting upwards
- drag- acting against the movement
- friction- the resistance that one surface or object encounters when moving on another
what is the equation for force?
force= mass x acceleration
what is friction?
friction is a force that opposes motion
what are the forces acting on a falling object and why does it reach terminal velocity?
when first an object is falling it is accelerating- the force acting downward (gravity) is larger than the force acting upward (air resistance). But when the forces balance out and become equal the object will have reached its maximum speed; its terminal velocity
describe an experiment to investigate the forces acting on a falling object
dropping parachutes from a given height; this shows us that gravity is acting on them. By increasing the size of the parachute and recording the results we can see that air resistance also has an effect on falling objects; plotting a graph should see that bigger surface area takes more time, from which we can infer that air resistance acts on falling objects
what are the factors affecting stopping distance?
- the condition of the driver; drugs/ tiredness (thinking distance)
- how worn the brakes/ tyres are
- if the weather conditions are poor
- how heavy the car is
- the speed the car is travelling at
what is the equation for moments?
moment= force x distance from pivot
where does the weight of the body act?
through the centre of gravity
describe an experiment to investigate how extension varies with applied force for helical springs, metal wire and rubber bands
- attach a spring to a newton meter and measure its length
- add a 50g weight and measure again
- continue to add another weight and take another measurement
- do this up to 400g
By plotting a graph from the results from this you can see the extension increases with force; as each time a new weight is added the spring gets longer
how does the initial region of a force-extension graph associate with hooke's law?
a force extension graph shows how much a material stretches for the force applied. The initial linear region is the straight diagonal showing a linear correlation between force and extension meaning that they increase at the same rate. This is hooke's law
But at some point the graph will begin to curve, this is when an object reaches its elastic potential
what is elastic behaviour?
the way at when you stretch an object with this behaviour it will return to its original shape after the forces stretching it have been taken away. Eg. when you stretch an elastic band and you let go it pings back to its original shape
what are the hazards of frayed cables?
in frayed cabling the insulation has worn down exposing the live wires, electricity can be conducted from these
what are the hazards of long cables?
longer cables are at a risk of being damaged and there is more resistance with long wires making them more at risk with overheating
what are the hazards of damaged plugs?
damaged plugs create a risk that some of the safety features may be broken
what are the hazards of water around sockets?
water conducts electricity and can cause energy from the circuit to flow through it creating a fire and electrocution risk. Metal objects in sockets have the same dangers
what are the uses of insulation and double insulation in domestic appliances?
insulation is covering a live wire with a material that won't conduct electricity
double insulation is a precaution that makes sure the live wire cannot touch the casing (so no shock can be conducted) usually by putting extra insulation around that wire. Double insulation can also mean that the casing of an object is plastic so even if the wires touch it, it won't conduct
what is the use of earthing for domestic appliances?
an earth wire is touching the case so that if a current is in the case, it will be directed through the earth wire, this will then take the current to the earth. Additionally the surge of electricity in the wire may break the fuse
what is the use of fuses in domestic appliances?
fuses are section of wire in the circuit that melt if too high a current goes through them. They come with different maximum currents
what is the use of circuit breakers in domestic appliances?
circuit breakers have an electromagnet that is activated if the current goes above a certain limit. The electromagnet pulls an iron switch towards it, this opens the switch and breaks the circuit
what is the equation for power?
power= current x voltage
what is the equation for energy transferred?
current x voltage x time
what is direct current?
direct current flows in one direction only. It is supplied by cells and batteries. It comes out as a straight line on an oscilloscope
what is alternating current?
alternating current changes from one direction to another rapidly. Mains electricity is alternating
what is a series circuit useful for?
in a series circuit everything is connected on one line. This means that the voltage is shared out between every component: this makes it useful for supplying low power things like fairy lights