A student connects a resistor directly across a battery whose voltage remains…
MATHEMATICS · Multi-part · ISC · Physics · Current Electricity · Ohm's law, V-I graphs and ohmic/non-ohmic conductors
Problem
A student connects a resistor directly across a 9.0V battery whose voltage remains practically constant during use.
(i) Starting from the expressions for electrical power and for potential difference across a resistor, derive a formula that expresses power only in terms of the potential difference across the resistor and its resistance.
(ii) Using the formula obtained in (i), determine the minimum resistance that must be chosen so that the power dissipated in the resistor does not exceed 0.45W.
(iii) If a resistor of the value found in (ii) is connected to the battery for 2minutes, calculate the electrical energy converted into heat in the resistor during this time.