Holooly Plus Logo
Holooly Plus Logo

Question Checkup 30.1.2: The magnetic field exerts forces on charged particles, but i......

The magnetic field exerts forces on charged particles, but is incapable of doing work on them. Why?

Step-by-Step
The 'Blue Check Mark' means that this solution was answered by an expert.
Learn more on how do we answer questions.
Report Answer

Since the magnetic force is always perpendicular to the velocity v = ds/dt , it is always perpendicular to the displacement ds .

Thus the incremental amount of work, d W= F \cdot d s =F d s \times \cos \theta , is always zero, and so the magnetic field can do no work.

Related Answered Questions

Question: Checkup 30.3.4

For the two loops in Figs. 30.13 and 30.14, what is the direction of the magnetic moment vector? ...

Verified Answer:

The magnetic moment vector is always perpendicular...
Question: Checkup 30.3.2

The torque given by Eq. (30.17) is zero at θ = 0° and at θ = 180°, so the loop is in equilibrium. Is the equilibrium stable at 0°? At 180°? ...

Verified Answer:

From \theta = 0°, a small displac...
Question: Checkup 30.3.1

The torque given by Eq. (30.17) has a maximum magnitude at θ = 90° and at θ = -90°. What is the direction of the torque on the loop shown in Fig. 30.14 for θ = 90°? For θ = -90°? ...

Verified Answer:

For \theta = 90°, the direction o...
Question: Checkup 30.2.3

A wire hangs in a horizontal magnetic field, held taut by a weight (see Fig. 30.12). We connect this wire to a battery, so a current flows vertically upward. The deflection of the hanging wire will be (A) To the right (B) To the left (C) Into the page (D) Out of the page (E) Zero ...

Verified Answer:

B) To the left. From F = IL \times B [/lat...
Question: Checkup 30.2.2

A straight wire carrying a current is placed in a uniform horizontal magnetic field. For what orientation of the wire is the magnetic force on the wire zero? ...

Verified Answer:

If the wire is straight, the force will be zero wh...
Question: Checkup 30.2.1

A power cord for an electric appliance consists of two parallel straight wires carrying currents in opposite directions. Is the magnetic force between them attractive or repulsive? ...

Verified Answer:

The force on them is repulsive. Recall from Eq. (2...
Question: Checkup 30.1.5

Two protons are moving in the same uniform magnetic field. The orbital radius of the first proton is 10 cm, and the orbital radius of the second is 20 cm. Which proton has the larger speed? Which has the larger orbital frequency? (A) First, first (B) First, second (C) Second, first (D) Second, ...

Verified Answer:

(E) Second, both same. As in Question 1, the large...
Question: Checkup 30.1.4

Can electrons be accelerated in a cyclotron? In what regard does a cyclotron used for electrons differ from one used for protons, if the magnetic field is the same? ...

Verified Answer:

Yes, any charged particle could be accelerated in ...
Question: Checkup 30.1.3

A proton and an electron are moving in a uniform magnetic field. Which has the larger cyclotron frequency? ...

Verified Answer:

Since the cyclotron frequency is f=q B / 2...
Question: Checkup 30.1.1

Two electrons are moving in a uniform magnetic field. One has an orbital radius of 15 cm. The other has twice the speed of the first. What is its orbital radius? ...

Verified Answer:

The radius of circular motion for a charged partic...