Practice Test 2 - AP Physics C Electricity and Magnetism

19 questions. Answer them in any order, then submit to see your score and every explanation.

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1. A solid conducting sphere of radius $R$ holds a net charge $+Q$ and is in electrostatic equilibrium. How much work is done by an external agent to move a test charge $+q_0$ from one point on the surface of the sphere to another point on the surface?
2. A square conducting loop is moved at a constant velocity $\vec{v}$ from a region of no magnetic field into a region with a uniform magnetic field $\vec{B}$ directed into the page. The velocity vector is perpendicular to the boundary of the field and to one side of the loop. What is the direction of the magnetic force on the loop as it enters the field?
3. A charged-particle lens uses a uniformly charged disk of radius $R=0.10\,\text{m}$ with surface charge density $\sigma=+4.0\,\mu\text{C/m}^2$; the on-axis electric field at point $P$ a distance $z=0.050\,\text{m}$ from the disk center is required to estimate focusing strength in $\text{N/C}$. The disk lies in the $y$–$z$ plane and its axis is the $x$-axis, with $P$ on $+x$. Assume vacuum and a thin disk. Consider the setup described above. Calculate the electric field at point P on the axis of the charged disk.
4. The charge on a capacitor in a charging RC circuit is given by the function $Q(t) = (10 \, \mu\text{C})(1 - e^{-t/(2.0\text{ s})})$. What is the current $I(t)$ flowing into the capacitor at $t=0$?
5. Two wires of identical length and diameter are connected to identical batteries. Wire 1 is made of copper ($\rho_C \approx 1.7 \times 10^{-8}\,\Omega \cdot \text{m}$) and Wire 2 is made of nichrome ($\rho_N \approx 1.1 \times 10^{-6}\,\Omega \cdot \text{m}$). How does the current $I_C$ in the copper wire compare to the current $I_N$ in the nichrome wire?
6. In an oscillating ideal LC circuit, the total energy is constant. At the instant the charge on the capacitor is at its maximum positive value, which of the following statements is true?
7. In the circuit shown, two loops share resistor $R_3$. The left loop contains a $9\,\text{V}$ battery and $R_1=3\,\Omega$. The right loop contains a $6\,\text{V}$ battery and $R_2=2\,\Omega$. The shared resistor is $R_3=4\,\Omega$. Currents $I_1$ (left loop) and $I_2$ (right loop) are clockwise. Find the current through the branch containing resistor $R_3$ (take downward through $R_3$ as positive), using Kirchhoff's Loop Rule. Use the diagram for loop identification and sign convention.
8. A charge of $+q$ and a charge of $-2q$ are located on the x-axis at $x=0$ and $x=d$, respectively. How much work must an external agent do to bring a third charge of $+3q$ from infinity to the point $x=2d$ on the x-axis?
9. Two dielectric slabs with dielectric constants $κ_1$ and $κ_2$ completely fill the space between the plates of a parallel-plate capacitor. The slabs have equal thickness and are arranged in parallel (side by side). What is the effective dielectric constant of this configuration?
10. A battery has an emf $\mathcal{E}$ and an internal resistance $r$. It is connected in series with an external resistor of resistance $R$. What is the total power supplied by the source of emf?
11. A flat, circular loop of area $A$ is placed in a uniform electric field of magnitude $E$. What is the electric flux through the loop when the plane of the loop is parallel to the electric field lines?
12. When the switch $S$ is closed, how does the behavior of the circuit change compared to when the switch is open?
13. A particle with charge $q$ and mass $m$ is accelerated from rest through a potential difference $V_0$. It then enters a uniform wire of length $L$ and cross-sectional area $A$, becoming one of the charge carriers. This single particle's contribution to current depends primarily on which property derived from its initial acceleration?
14. An initially unmagnetized sample of a material is placed in a strong external magnetic field. The sample becomes strongly magnetized and retains a significant amount of its magnetism after the external field is removed. This material is best classified as:
15. A uniform electric field $E=1.2\times10^{3}\,\text{N/C}$ points upward. Points $A$ and $B$ are separated vertically by $d=0.50\,\text{m}$, with $B$ above $A$. Use $\Delta V=V_B-V_A=-Ed$. Based on the data, calculate the potential difference between points $A$ and $B$.
16. The potential difference $V$ across a circuit component is measured as a function of the current $I$ through it. A plot of $V$ as a function of $I$ results in a straight line passing through the origin with a slope of $200\,\text{V/A}$. What is the resistance of the component?
17. A $150$-turn loop ($A=0.030\ \text{m}^2$) in $B=0.20\ \text{T}$ rotates at $f=10\ \text{Hz}$; what induced EMF magnitude?
18. System A consists of two protons separated by a distance $d$. System B consists of a proton and an electron separated by a distance $d$. System C consists of two electrons separated by a distance $d$. Let $U_A$, $U_B$, and $U_C$ be the electric potential energies. Which option correctly ranks the potential energies?
19. Which of the following statements about electric field lines is correct?

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