q v B The force on a moving charge in a magnetic field is related related to its charge and velocity.

Right hand ‘Slap’ rule fingers ~ field Thumb ~ velocity of a charged particle Slap – force direction

Fleming’s left-hand motor rule

A proton is at rest at point P A proton is at rest at point P. The direction of the magnetic force on the proton is best represented by: A. B. C. D. E. None of these Choice One Choice Two Choice Three Choice Four Choice Five Choice Six P

Since it’s difficult to draw in 3-D, adopt the following symbols: x x’s indicate a B-field into the page dots indicate a B-field out of the page (hint: just think of arrows: )

In the following examples, is the charge + or - ?

B Field out of screen proton Which free body diagram represents the moment when the proton enters the magnetic field region? Construct a free body diagram that represents the moment when the proton enters the magnetic field region. 1 2 p on earth F r 3

Which motion diagram matches the above description? An electron is moving to the right at a constant speed and enters a magnetic field that is pointed towards the right. Which motion diagram matches the above description? Construct a motion diagram that matches the above description. 1 3 4 2 5

Work done by the Magnetic Force x + v F s F F s s Work = (Fcos)s = ? The work done by the Magnetic Force is equal to _____ The speed of a charge in a Magnetic Field is ______

Circulating Charged Particle When the charge moves perpendicular to the B-field, we can show that: Momentum What path does the charge follow if v is not perpendicular to B? Web Link: Helix

Which pictorial representation matches the above description? An electron is moving to the right across a magnetic field that is coming out of the page. Which pictorial representation matches the above description? Construct a pictorial representation that matches the above description. 1 2 3 4 No picture represents this situation accurately.

- An electron in a magnetic field moves at a speed of 1.3 x 106 m/s in a circle of radius .35 m. Find the magnitude and direction of the magnetic field.

Determine the magnitude and direction of the force on an electron traveling horizontally to the east in a vertically upward magnetic field of strength 0.75 T. east north Direction?

Alpha particles of charge +2e and mass of 6 Alpha particles of charge +2e and mass of 6.6 x 10-27 kg are emitted from a radioactive source at a speed of 6.6 x 10-27 m/s. What magnetic field strength would be required to bend them into a circular path of radius of 0.25 m? r B v

Electric and Magnetic Fields x B E - v As the electron enters the crossed fields: The Electric Field deflects it in what direction? The Magnetic Field deflects it in what direction? If E and B are adjusted so that the electron continues in a straight line… Web Links: TV Screens

What is the velocity of a beam of electrons that go undeflected when passing through perpendicular electric and magnetic fields of magnitude 8.8 x 103 V/m and 3.5 x 10-3 T, v respectively? What is the radius of the electron orbit if the electric field is turned off?