Quick questions on Charges in magnetic fields explained: HSC Physics Module 6

4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is the Lorentz force?

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A particle of charge

q

moving with velocity

\vec{v}

in a magnetic field

\vec{B}

experiences a force:

What is q1?

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Write the equation for the force on a charge

q

moving with velocity

\vec{v}

in magnetic field

\vec{B}

and state the direction of the force when

\vec{v} \perp \vec{B}

. [2 marks]

What is q2?

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A proton enters a

0.20 \text{ T}

field perpendicular to its velocity at

4.0 \times 10^6 \text{ m/s}

. Calculate the radius and period of its circular motion. [4 marks]

What is q3?

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A velocity selector uses crossed

\vec{E}

and

\vec{B}

fields, with

E = 5000 \text{ V/m}

and

B = 0.020 \text{ T}

. (a) Show that only particles with

v = E/B

pass through undeflected. (b) Calculate this selected speed.

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