Physics Major Flashcards
What is resistance measured in?
Ohms
Resistance
Measure of the DIFFICULTY the charges have in moving through a circuit.
Factors which affect resistance
Length
Substance
Temp
Thickness
High resistance - _______ current
Low
Low resistance - ________ current
High
As the length of the wire increase, resistance _____
Increases
As the thickness increases, the resistance _______
Decreases
Highest resistance wife
Nichrome
Lowest resistance wire
Gold
As the temperature increases, the resistance ?
Increases
Conditions for wire to have small resistance
Short, thick, gold, cold
Wire to have high resistance
Long, thin, nichrome, hot
Advantage of parallel circuits
Independent control of lights ( if one breaks, others still function)
Advantages of series circuits
Cheaper
Energy efficient
Eg of series lights
Christmas lights
Eg of parallel lights
House lights
Car lights
Total resistance of resistors in series
All resistance added up
Total resistance of Parallel resistors
Total resistance is less than the resistance of the lowest resistor
Types of energy
Electrical energy Kinetic Heat Light Sound
Conditions of electrocution
Touching two conductors
Different electrical potentials
Active wire
Wire that carries electricity to the house and different parts of the house
Neutral wire
Carrys back 0v of electricity to the power station to complete circuit
Double insulation
Each wire has two layers of insulation around it
When is two pin plug used
Use of appliances with insulating cases
When is three pin plug used
Appliances with metal casings
Color of active wire
Red or brown
Color of neutral wire
Blue or black
Color of earth wire
Green or yellow
Fuse
Breaks a circuit by melting when a large current passed through it
Circuit breaker
Excessive current trips the switch and break circuit
Earth wire
Low resistance wire that connects metal frames of electrical appliances to the ground
Safety switch
When a large difference in current us detected flowing through the active and current wire, the switch breaks so person isn’t electrocuted
Cost of electricity can be ccated by
Cost = power x time x 30 cents
1kw = W
1000 w
What happens when too much current flows in an elect magnetic circuit breaker
Cool creates a large magnetic fis which attracts the iron and breaks circuit
