6. A uniform magnetic field of B = 0.5 T is directed as...

6. A uniform magnetic field of B = 0.5 T is directed as shown. Calculate the force on a proton moving in the direction shown in each figure. Draw the direction of the force and determine its magnitude. A.) B is into the paper, and v is to the right: B = 0.5 T v = 2×10? m/s B.) B is to the right, and v is into the paper: B = 0.5T v = 2×10? m/s 7. Repeat the answers to problem 6, above if the charged particle is an electron. Draw the direction of the magnetic field, velocity, and force for each part.

Transcript

00:01 So here we have a question on a proton moving in a magnetic field and we're asked to calculate the direction of the force and determine the magnitude of the force.

00:09 So i've drawn the scenarios here, scenario a and b, and i've also drawn the relevant hand positions using fleming's left hand rule.

00:19 So these are hands, believe it or not.

00:20 My art skills are awful.

00:23 But hopefully i can get the idea across.

00:26 So thumb, first finger, second finger or middle finger, and then thumb, first finger, middle finger.

00:34 So let's have a look at the first question.

00:37 So, what, scenario a.

00:39 If we have a field, so fields into the page, so this is the first finger going into the page.

00:47 And the current, the current is the, if the protons going from left to right, current is the direction that positive charge flows.

00:54 And that's going to be important for later on.

00:58 But the current will be in the same direction as the direction of movement of the proton.

01:03 So that's going to be from left to right.

01:05 That leaves our thumb pointing upwards.

01:07 So we're going to have the force upwards, up the page.

01:12 So that's going to be force.

01:14 And let's work out the magnitude of it.

01:15 So we can use f is equal to b, qv.

01:19 And then we substitute in all our values.

01:21 0 .5.

01:21 The charge of the proton is 1 .6 times 10 to the minus 19.

01:25 And then the velocity is 2 times 10 to the 5, and that's going to get you to 1 .6 times 10 to the minus 14 newtons upwards.

01:37 Okay, then what about the second scenario? well, now we have the field, so this is the first finger.

01:44 So thumb is downwards, but the first finger going from left to right, the current's going into the page, and that leaves your thumb, which is the direction of the force, pointing downwards...

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