Question

A copper bar is allowed to slide freely back and forth across two horizontal copper rails. The bar never loses contact with the rails. (a) If the magnetic field strength is uniform as shown with a field strength of 1 Tesla, what is the current in the 1000 Ohm resistor over time as a function of the speed of the bar away from the resistor? answer will in parametric (equation) form. (b) For a specific speed of 1 meter/second, what is the voltage across the resistor? (c) Re-draw the figure and indicate the polarity of the emf across the resistor for the motion shown. (Note: The bar never travels so far as to leave the field)

Answer 1

There is no figure, but I'll give the answer with general equations and you'll apply to the concrete case:

(a)

l=length of the copper bar sliding on the rails (no numerical value provided by the text)

Minus counts for the sense of the e.m. tension relative to the sense of magnetic flux variation.

(If you know l, just replace the other numbers and make the calculus)

(b)

Use eq (1) and replace the numbers.

(c) For the sense, use the right hand rule:

(the line along the middle finger is the conductor/bar sliding on the rails)