MATHEMATICS · Multi-part · ISC · Physics · Current Electricity · Ohm's law, V-I graphs and ohmic/non-ohmic conductors
Problem
Three resistors R1=4Ω, R2=6Ω and R3=12Ω are connected to a 9V source.
(a) The resistors are first connected in parallel.
(b) They are then connected in series.
Answer the following questions for the two cases.
(i) For case (a), derive an expression for the power dissipated in any one resistor in terms of the supply voltage V and its resistance R. Do not use numerical values in this step.
(ii) Using the expression obtained in part (i), calculate the power dissipated in each resistor when connected in parallel.
(iii) Explain, with suitable reasoning and reference to your results, why the smallest resistance receives the greatest power in the parallel connection whereas the largest resistance receives the greatest power in the series connection.