a battery of emf $($E$)$ is connected in series with the resistor in example $27\mathrm{.}4.$ The bar is initially at rest $,$ and now there's nothing pulling it$($a$)$ Find an expression for the initial value of the current in the circuit.$($b$)$ The bar eventually reaches a constant speed. Find an expression for this speed.$($c$)$ what's the current in the circuit once the bar is moving at constant speed?