Wednesday 29 February 2012

Electrical systems 28/02/2012


Electrical Systems
·         Ohms law: ohms law states that the potential difference (volts) is equal to the resistance (ohm) multiplied by the current (amps).
·         Therefore :
            V = I x R
            
                R = V / I
            
                I = V / R

Series and parallel

If batteries are connected in series the volts add up but the amps stay the same

If batteries are connected in parallel the volts stay the same but the amps add up

When resisters are connected in series the ohms add up and in parallel the ohms are worked out using the formula  Rt = (R1 x R2) / (R1 + R2) 

If components are connected in series the volts is the sum of the drop over the resistance the current stays the same throughout the circuit. If the components are connected in parallel the voltage is the same for all the components but the current drops.

Measuring ohms, amps and volts using a multimeter

1.      Check that the cables are in the right ports (indicated by labels)
2.      Set the multimeter to the right setting
3.      For the potential difference (volts) connect the cables in parallel to the component that needs to measured
4.      For the current (amps) connect the cables in series  to the circuit
5.      When using the ohm setting to measure the resistance make sure that all the power is disconnected from the component to be measured, if not the multimeter may get damaged.
Health and safety
·         Always follow the warning signs and wear the right protective equipment
·         Look out for hazards while working and either solve the problem or tell someone who can
·         Beware of poisonous fumes that are given off while working on a car
·         Do not expose your skin to car oil for long periods of time, wear gloves or a barrier cream
·         Beware of hot engine/car parts
·         Do not work under car that is only jacked up, use axel stands
·         Be careful when working with fuel lines that are under pressure
·         Wear safety glasses  when working under cars

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