CALCULATING ELECTRICITYTODAY WE ARE GOING TO LOOK AT

•CURRENT•VOLTAGE•RESISTANCE

Ok lets begin

Look at this video below lets see what we learn• http://www.youtube.com/watch?v=KvVTh3ak

5dQ&feature=related

“Answer me this”

• From the video look at the following questions– Can you define current– Can you define voltage– Can you define resistance– What are the units of measurement of each

Current

• Current is the flowing of negative charges from one point to the other

• The symbol for current is I• The unit of measurement of current is amperes(amps)• Current is measured using an ammeter

Voltage

• The force or energy involved in pushing the charges around is referred to as E.M.F.

• Across electrical components there are energy differences called Potential difference or VOLTAGE

• The symbol for Voltage is V• The unit of measurement is Volts(V)• Voltage is measured using a voltmeter

Resistance

• Resistance is the opposing of the flowing of current

• The symbol of resistance is R• The unit of measurement is Ohms(Ω)• Resistance can be measured using a

multimeter however R can be calculated

The Relationship between I, V & R

• Well some dude came up with this law that makes us calculate R

• Ohms law- the current flowing in a conductor maintained at a constant temperature is proportional to the potential difference(voltage) between its ends

• Well all that means is simply V= IR

“The triangle to remember”

Let’s practice

• Calculate the current flowing through a circuit is the voltage is 9 V and the resistance is 3 ohms.

Ok Good effort , here’s my answer

• What do I want to find– Current-I

• What do I have – V=9V & R=3Ω

• What do I know– V=IR

• Then I solve• 9=I * 3• I= 9/3• I= 3 A

Let’s practice

• Calculate the voltage flowing through a bulb if the current passing through it is 15 A and the resistance of the bulb is 3Ω.

Ok Good effort , here’s my answer

• What do I want to find– Voltage-V

• What do I have – I=15A & R=3Ω

• What do I know– V=IR

• Then I solve• V=15*3• V=45V

Let’s practice

• Calculate the resistance in a circuit if the voltage of the power supply is 4.5 V and the current flowing through is 1A

Ok Good effort , here’s my answer

• What do I want to find– Resistance-R

• What do I have – I=1A & V=4.5V

• What do I know– V=IR

• Then I solve• 4.5=1*R• R=4.5/1• R=4.5Ω

Why do we need this

• Understanding values helps know how much electricity is required to make something work

• It helps us to determine safety since can calculate the amount of electricity flowing through an electrical component so this would not happen to us

• http://www.youtube.com/watch?v=M4qzMbpy0ks

Current in parallel and series

• Series – Current flowing through components in series is

the same through each component• Voltage – Current flowing through a parallel circuit splits up

and recombine at the connecting points

Voltage in series and parallel

• Series – The voltage across components in series is

different because “potential difference” charges across each component

• Parallel– The voltage is the same across things in parallel

JUST FOR YOUR REVIEW

• http://www.youtube.com/watch?v=bnzmVAa46xg&feature=fvwrel

• http://www.youtube.com/watch?v=LOEiA9yAh6E&feature=related