1. Bellwork A wire carrying a current of 3.0 A is in a uniform magnetic field. The wire makes an angle of 15° with the field. The wire is 35 cm in length and the force on the wire is 0.80 N. What is the strength of the magnetic field?

2. Force on a Charged Particle Charged particles are not confined to a wire. Cathode-ray tube in monitors and TVs use magnetic fields to deflect electrons to form pictures on the screen. The screen in coated with phosphor to glow when an electron hits it.

4. The force produced by a magnetic field on a charged particle depends on it’s velocity, it’s charge (+/-), and on the strength of the field. Direction of force is perpendicular to both the velocity of the particle and the B-field. F= Bqv B- magnetic field (T) q- charge of particle (C) (no negatives) v- velocity of particle (m/s)

5. To determine directions: Use the 2nd RHR: Thumb point in the direction of the velocity Fingers faces the direction of the field Your palm points to the direction of the force on a POSITIVE particle. It will be opposite for a NEGATIVE particle.

6. Practice A proton travels at 3.0 x 10 6 m/s to the west through a uniform magnetic field of 0.04 T toward the north. What is the force on the proton?

7. An electron travels at 2.7 x 10 5 m/s to the west through a uniform magnetic field of 0.07 T toward the north. What is the force on the electron?

8. Review 1 st RHR Magnetic Field Lines F = BIL 2 nd RHR F = Bqv 3 rd RHR