Q: A uniform magnetic field of $$0.80\ T in $$the negative $$z-$$direction is present. An electron is projected with $$v_0 = 9.1$$ \times $$10^6$$\ m/s$$ in the +x$-direction and passes through without deflection. What is the electric field vector in the region?

$$-7.3 \times 10^6$\ V/m\ \hat{y}$$

Question 1

A wire of length $$L$$ and radius $$r$$ has a resistance $$R. If $$the radius is doubled while keeping the length and material the same, what happens to the resistance?

Accepted Answer

$$R/4$$

Question 2

A 0.15 mm diameter wire made of a metal with resistivity $$1.68 	imes 10$$^{-8}$$\ \Omega \cdot m is to $$have a resistance of $$15\ \Omega. $$What length of wire is required?

Accepted Answer

$$16\ m$$

Question 3

A device delivers a current of $$5.0\ A$$ for $$10\ s. $$How many electrons pass through the device in this time? ($$e = 1.602 	imes 10$$^{-19}$$\ C)$$

Accepted Answer

$$3.1 	imes 10$$^{20}$$

Question 4

A cylindrical wire of length $$40.0\ m$$ and radius $$4.00\ mm is $$connected to a $$16.0\ V$$ source. The resistivity of the metal is $$1.68 	imes 10$$^{-8}$$\ \Omega \cdot m. $$What is the current through the wire?

Accepted Answer

$$1200\ A$$

Question 5

A $$100\ W$$ light bulb is connected to a $$110\ V$$ source. What is the resistance of the bulb?

Accepted Answer

$$120\ \Omega$$

Question 6

In the circuit with four identical resistors (A, B, C, D) and two switches $$S_1$$ and $$S_2$$, which action results in the greatest current through resistor A?

Accepted Answer

Closing both switches

Question 7

For the circuit shown with resistors $$0.75\ \Omega$$, $$1.0\ \Omega$$, $$2.0\ \Omega$$, $$5.0\ \Omega$$, and $$10\ \Omega$$, what is the equivalent resistance?

Accepted Answer

$$3.0\ \Omega$$

Question 8

In the circuit with $$3.0\ \Omega$$, $$4.0\ \Omega$$, $$5.0\ \Omega$$, $$2.0\ \Omega$$, and $$1.0\ \Omega$$ resistors and a $$12\ V$$ battery, if the equivalent resistance is $$4.28\ \Omega$$, how much current passes through the $$1.0\ \Omega$$ resistor?

Accepted Answer

$$2.8\ A$$

Question 9

For the same circuit, how much current passes through the $$3.0\ \Omega$$ resistor?

Accepted Answer

$$1.2\ A$$

Question 10

In the circuit with capacitors and resistors, just after closing the switch $$S$$, what is the current in the $$15.0\ \Omega$$ resistor?

Accepted Answer

$$0.00\ A$$

Question 11

After the switch $$S$$ has been closed for a very long time, what is the potential difference across the $$28.0\ \mu F$$ capacitor?

Accepted Answer

$$25.0\ V$$

Question 12

A horizontal wire carries a current straight toward you. From your point of view, the magnetic field at a point directly below the wire points:

Accepted Answer

To the right

Question 13

A very long thin wire produces a magnetic field of $$0.0050 	imes 10$$^{-3}$$\ T at a $$distance of $$3.0\ mm$$ from the wire. What is the magnitude of the current in the wire? ($$\mu_0$ = 4\pi 	imes 10$$^{-7}$$\ T\cdot m/A)$$

Accepted Answer

$$7.5\ mA$$

Question 14

Three particles travel through a region of space where the magnetic field is out of the page. The electric charge of each of the three particles is, respectively:

Accepted Answer

1 is negative, 2 is neutral, and 3 is positive.

Question 15

A charge is accelerated from rest through a potential difference $$V$$ and then enters a uniform magnetic field perpendicular to its path, moving in a circle of radius $$R. If $$the accelerating potential is tripled to $$3V$$, what will be the new radius?

Accepted Answer

$$\sqrt{3}R$$

Question 16

A negatively charged particle is moving to the right, directly above a wire with current to the right. In which direction is the magnetic force on the particle?

Accepted Answer

Upward

Question 17

An electron moves at $$8.0 	imes 10^6$\ m/s$$ along the $$+x-$$axis and enters a region with a $$2.5\ T$$ magnetic field at $$60^\circ to $$the $$+x-$$axis in the $$xy-$$plane. What is the magnitude of the magnetic force on the electron? ($$e = 1.602 	imes 10$$^{-19}$$\ C)$$

Accepted Answer

$$2.8 	imes 10$$^{-12}$$\ N$$

Question 18

A uniform magnetic field of $$0.80\ T in $$the negative $$z-$$direction is present. An electron is projected with $$v_0 = 9.1$$ 	imes $$10^6$$\ m/s$$ in the +x$-direction and passes through without deflection. What is the electric field vector in the region?

Accepted Answer

$$-7.3 	imes 10^6$\ V/m\ \hat{y}$$

Question 19

A wire carries a $$4.0\ A$$ current along the $$+x-$$axis through a uniform magnetic field $$\vec{B} = (5.0\ \hat{x} + 7.0\ \hat{y})\ T. If $$the wire experiences a force of $$30\ N$$, how long is the wire?

Accepted Answer

$$1.1\ m$$

Question 20

If the current density in a wire of radius $$R is $$given by $$J = kr$$, $$0 \u003c r \u003c R$$, what is the total current in the wire?

Accepted Answer

$$2\pi k R^3$/3$$

PHY 131 Practice Exam 2 – Step-by-Step Physics Guidance

Study Guide - Practice Questions

Study Guide - Flashcards