Ohms law

V = IR

describes the relationship between the voltage V across a resistor, the electrical current I

passing through the resistor and the resistance R. Usually voltage is measured in volts,

current is measured in amperes (amps), and resistance is measured in ohms, where 1

ohm = 1 volt/amp.

(a) Take the derivative of Ohms law to find an equation relating dV/dt, dI/dt and dR/dt .

Now suppose that the voltage across the resistor is held constant at 20 volts, while the

resistance is steadily increased at a rate of 0.4 ohms/sec.

(b) What is the current through the resistor when the resistance reaches 10 ohms?

(c) At what rate is the current changing at that time?