91Ó°ÊÓ

Is the direction of an electric current from the positive terminal of a battery to the negative terminal or from the negative terminal to the positive terminal? Explain.

An ammeter can measure currents as small as \(12 \mathrm{pA}\). How many electrons per second flow through a wire with a 12-pA current? (Recall that \(1 \mathrm{pA}=10^{-12} \mathrm{~A}\).)

A charge of \(12 \mathrm{C}\) flows past a given point in the time \(\Delta t\). If the current produced by the charge is \(0.15 \mathrm{~A}\), what is \(\Delta t\) ?

How much time is required for \(0.25 \mathrm{C}\) of charge to flow through a wire carrying a current of \(1.1 \mathrm{~A}\) ?

A battery does \(59 \mathrm{~J}\) of work as \(6.6 \mathrm{C}\) of charge passes through it. What is the voltage of the battery?

How much charge passes through a \(12-\mathrm{V}\) battery that does \(41 \mathrm{~J}\) of work?

A current of \(2.2\) A flows through a \(140-\Omega\) resistor. What is the potential difference applied to the resistor?

What current flows through a \(210-\Omega\) resistor when a potential difference of \(15 \mathrm{~V}\) is applied to it?

A current of \(3.2\) A flows through a resistor when a potential difference of \(95 \mathrm{~V}\) is applied to it. What is the resistance of the resistor?

Pacemakers designed for longterm use commonly employ a lithium-iodine battery capable of supplying \(1500 \mathrm{C}\) of charge. If the average current produced by the pacemaker is \(5.6 \mu \mathrm{A}\), what is the expected lifetime of the device?