Download Electric Force - Parkland College

Magnetic Force/Field
Magnetic Field
• North/South Pole
• Opposites attract
• Unit: Tesla (T)
• Field lines point in direction that a North Pole
would feel a force
Earth behaves magnetically as if a bar
magnet was located near its center
Magnetic Force on a moving Charge
• 1. Charge must be moving
• 2. Velocity must have a component perpendicular to the
direction of the magnetic field
Direction of Force is
perpendicular to both
velocity and field
RHR #1
Fingers = B Field
Thumb = velocity or current
Palm = Force
Why? (such a weird direction)
What happens near the poles where
the charges are not deflected?
Force on a moving Charge
F = B * qo(v sin θ) (N)
• What is the force on a 2μC charge moving at 4.3x104 m/s
perpendicular to a 0.4 T magnetic field?
A proton (m= 1.67x10-27 kg, q= 1.6x10-19 C) is moving with a
velocity, v= 6.3x10-5 m/s, and enters a region with a magnetic
field of 0.4 T. What is the radius of the circle that the charge will
move through? What is the final velocity of the charge?
Force on a current in a wire:
F = I l B sin(θ)
• A square loop (10cm) of wire has a current of 5A flowing
clockwise and is placed in a 0.4T magnetic field directed into
the page. What is the magnitude and direction of the force
on each segment of the loop?
X X X X X X
X X X X X X
X X X X X X
X X X X X X
X X X X X X
Torque on a loop:
t = N I A B sin(φ)
• A square loop (10cm) of wire has a current of 2A flowing
clockwise and is placed in a 0.75T magnetic field directed to
the right. What is the magnitude and direction of the torque
on the loop?
A square loop (10cm) of wire has a current of 2A flowing clockwise and
is placed in a 0.75T magnetic field as shown below. What is the
magnitude and direction of the torque on the loop?
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