In our basic model of a battery, we said that the force per unit charge the battery provides through chemical reactions ($\mathbf{f}$) had a magnitude equal the electric field produced by the separated charge ($\mathbf{E}$). This maintains a constant drift speed across the battery for the electrons. If the battery has some internal resistance ($r$), which is larger? 1. $|\mathbf{f}|$ 2. $|\mathbf{E}|$ 3. Both still the same Note: Correct answer: A

Surface Charge is Real

One end of rectangular metal loop enters a region of constant uniform magnetic field $\mathbf{B}$, with initial constant speed $v$, as shown. What direction is the magnetic force on the loop? <img src="./images/loop_entering_Bfield.png" align="left" style="width: 500px";/> 1. Up the "screen" $\uparrow$ 2. Down the "screen" $\downarrow$ 3. To the right $\rightarrow$ 4. To the left $\leftarrow$ 5. The net force is zero Note: * Correct Answer: D
One end of rectangular metal loop enters a region of constant uniform magnetic field $\mathbf{B}$, out of page, with constant speed $v$, as shown. As the loop enters the field is there a non-zero emf around the loop? <img src="./images/loop_entering_Bfield.png" align="left" style="width: 500px";/> 1. Yes, current will flow CW 2. Yes, current will flow CCW 3. No Note: * Correct Answer: A
A rectangular metal loop moves through a region of constant uniform magnetic field $\mathbf{B}$, with speed $v$ at $t = 0$, as shown. What is the magnetic force on the loop at the instant shown? Assume the loop has resistance $R$. <img src="./images/loop_in_Bfield.png" align="left" style="width: 500px";/> 1. $2L^2 vB^2/R$ (right) 2. $2L^2 vB^2/R$ (left) 3. 0 4. Something else/not sure... Note: * Correct Answer: C