Untitled Flashcards Set

Quantity 

Equation 

Current 

Current = charge ÷ time

I = Q / t

Resistance 

Resistance = potential difference ÷ current

 R = V / I

Voltage

Voltage = current x resistance 

V = I x R

Power

Power =current x voltage

 P = I x V

Since Voltage is also current x resistance,

 Power = current² x resistance

 P=I² x R

Power=Voltage² /Resistance 

P=V² /R

Energy

Energy = power x time 

E = P x t

E = I x V x t

E = Q x  V

Cost

Cost of electricity = number of kW h  x cost per kW h 

Resistance of a conductor

Resistance= constant ×lengthcross sectional area

R=ρLA

Current

Voltage

Resistance

Series

Same at all points

the total p.d. across the components in a series circuit is equal to the sum of the individual p.d.s across each component

R= R₁ + R₂ + R₃

The sum of the resistance 

parallel 

Sum of currents in the branches equals the total current entering or leaving the parallel branch

the p.d. across each branch of a parallel arrangement of components is the p.d. across the whole arrangement