Download 5F10-001 Ohm`s Law PROMPTS EMBEDDED STATEMENT OF THE

5F10-001
Ohm’sLaw
PROMPTSEMBEDDED
I
STATEMENTOFTHEPROBLEM:PowerandOhmsLaw
Atacticalradiorequires1.5ampsat12volts.Yourpower
supplywillprovidethenecessarycurrentbutthecables
connectingthesupplytotheradiohaveanintrinsic
resistanceof2ohmseach.Howmuchpowerislostinthe
cables?Whatmustthevoltageatthepowersupplybein
ordertoprovide12voltsattheradio?
STRATEGY
Power
Supply
R
Vsupply
Vradio Radio
R
I
Power (P) dissipated in a circuit component is proportionate to the voltage change (V) across that
component and the current (I) that flows across it 𝑃 = 𝐼𝑉. The voltage change is proportionate to its
resistance (R) and the current that flows across it 𝑉 = 𝐼𝑅.
IMPLEMENTATION
We will combine the two equations described above to get a relationship for power and then use ohms law
to determine the voltage of the power supply.
CALCULATION
𝑃 = 𝐼𝑉and𝑉 = 𝐼𝑅 Substituting for voltage gives 𝑃 = 𝐼 ! 𝑅
Since the resistors are in series the same current flows in each. We may add their resistances to get the total
resistance in the wires.
Solving for power dissipated in the resistors
𝑃 = __________________________ = 9 𝑤𝑎𝑡𝑡𝑠
In the space above, supply the missing numbers as you would enter them in your calculator, then
complete the calculation.
We may now calculate the voltage drop across the resistors
𝛥𝑉 = (1.5)(2.0 + 2.0) = 6 𝑣𝑜𝑙𝑡𝑠
Therefore the power supply must provide the 12 volts required by the radio and an additional 6 volts to
compensate for the losses in the cables. 𝛥𝑉 = 18𝑉