- Created by: Tom Belk
- Created on: 21-05-14 19:51
Electrical appliances waste some energy as heat.
Pd=current x resistance
Resistance= pd/current or R=V/I
Unit for resistance=Ω
Energy transferred= current x time x potential difference (itv)
Electrical power= energy transferred/time
Power= current x potential difference
Power= potential difference/ current
Power is measured in Watts or Kilowatts
1 watt of power means that 1 Joule of energy is used every second
The unit for current is the Amp (A). It is measured with an Ammeter.You can move the Ammeter to different places but the reading will same the same, unless you add more bulbs or batteries.
If a wire is moved across a magnetic field, a current is produced. This is called electromagnetic induction. Induction also occurs if a magnet is moved in a coil of wire, or if a coil of wire rotates in a magnetic field.
In all of these methods of inducing a current, the wire and magnetic field move perpendicular to each other. If they move parallel to each other, no current is induced.
How electricity is made: Fuel is burned to boil water at a high pressure. The boiling water produces superheated steam. The superheated steam turns a turbine. The turbine rotates a magnet in the generator. The rotating generator generates electricity-chemical, thermal, kinetic and then electrical.
%efficiency=useful energy output/ total energy input x100
average speed= total distance/ total time
acceleration= speed/ time
Friction can cause air resistance or drag. The size of the frictional force equals the applied force unless the applied force is bigger than the maximum value of the frictional force. If this is the case then the frictional force remains at the maximum possible value.
Work and Power
work done= energy tranferred
Joules= energy for work
work done= force x distance moved
power= work done/ time taken
The thickness of each arrow is proportional to the amount of energy involved at that stage.
Input on the left.
Heat energy(wasted) on the bottom.
Output on the right.
The units for density are g/cm3.
Density(P-Rho)= mass/ volume
Volume= mass/ density
mass=density x volume
The unit for pressure is the Pascal(Pa). It can also be written as N/m3
Area= force / area
Force= pressure x area
Pressure between liquids and solids= Pressure= density x gravity x height
All hydraulic systems use 2 pistons linked via a pipe carrying a special oil called hydraulic fluid.
Pressure= force applied/ area of master piston
Pressure= force exerted/ area of slave
Moment= force x distance from pivot
Moments are measured in Newton metres(Nm)
A car would topple if the centre of mass is on the outside of the wheel.
Force= spring constant x extension
Newtons=kg's x gravity-10m/s2