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Today4/7. Lab “Current Balance” Right Hand Rule for: Magnetic Force Magnetic field North Pole of a Current Loop Start reading Ch. 21. Magnetic Forces. Charges experience Magnetic Forces as well as Electric Forces. The Electric force is given by : F = qE.
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Today4/7 • Lab “Current Balance” • Right Hand Rule for: • Magnetic Force • Magnetic field • North Pole of a Current Loop • Start reading Ch. 21
Magnetic Forces Charges experience Magnetic Forces as well as Electric Forces. The Electric force is given by : F = qE The Magnetic force is given by : F = qvB sin v is the charge’s velocity, B is the magnitude (strength) of the Magnetic field, and is the angle between v and B. Direction of the Magnetic force is perpendicular to both v and B, and so there are two choices for the force direction
F big, out F smaller, in F smallest, in F big, in Magnetic Forces RHR A positive charge moves in a B-field that points to the right. What direction is the force on the charge for each case? F = qvB sin Fingers with B, thumb with v, force points in the direction of your palm. v F = 0 F = 0 B is the angle between v and B.
F = qvB sin F Magnetic Forces RHR A positive charge moves to the right in a B-field that points in the direction shown. What direction is the force on the charge? Fingers with B, thumb with v, force points in the direction of your palm. B v F is out of the page, still perpendicular to the velocity.
F = qvB sin = 0 Magnetic Forces RHR A positive charge moves to the right in a B-field that points in the direction shown. What direction is the force on the charge? The RHR makes no sense and there is no force on the charge. F = 0 v B
F I B Magnetic Forces, Wires Find the direction of the force on the wire placed in a B field. F = qvB sin F = IlB sin qv becomes Il
B Fields caused by ? The discussion so far has been about how charges respond to Magnetic fields, but what causes the Magnetic field? B-Fields are caused by moving charges, or currents. Wrap a wire around a nail-push current through the wire-produce a magnetic field
B Fields caused by Currents Compass needle and a wire
Due to wire 2 Due to wire 1 B Fields caused by Currents Two currents 1 2 Forces equal and opposite, 3rd law
Due to wire 2 Due to wire 1 B Fields caused by Currents Two currents 1 2 Forces equal and opposite, 3rd law
1 1 3 2 4 1 2 4 4 2 4 3 2 3 3 1 B Fields caused by Currents Current loops 1 4 2 3
B Fields caused by Currents The net field points one way inside the loop and the opposite way outside the loop. Current loops
B Fields caused by Currents Current loops
B Fields caused by Currents Current loops are magnets!!! Behave like magnets!!! S N
B Fields caused by Currents Current loops N S