# HW7 due on Friday Turn in HW6 Stand by to receive back HW5 EXAM 2 coming up on Monday !!!!! March 30 th.

## Presentation on theme: "HW7 due on Friday Turn in HW6 Stand by to receive back HW5 EXAM 2 coming up on Monday !!!!! March 30 th."— Presentation transcript:

HW7 due on Friday Turn in HW6 Stand by to receive back HW5 EXAM 2 coming up on Monday !!!!! March 30 th

Magnetic field due to a long (straight) wire: Let’s review:

current on ( I up ! ).

Right hand rule (#1)

( I up/out ! ). DIRECTION-OK MAGNITUDE???

Experiment shows: For a long straight wire

Example: Suppose a cable is carrying 100 A current. What’s the B-field 1 cm from the cable? How about 10 cm?

Example: The cables are each carrying 25 A out the of page. What’s at point Q? 13.0 cm Q

Example: The cables are carrying 25 A out the of page. What’s at point P? Superposition! Next … 13.0 cm P

P Example: The cables are each carrying 25 A out the of page. What’s at point Q?

P Now: Vector Superposition! Next …

Example: The cables are each carrying 25 A out the of page. What’s at point Q?

Forces between current-carrying conductors

Opposite Currents Repel!

Parallel Currents attract! (same magnitude as other case!)

Example: What force per unit length do two cables 1 cm apart produce on each other? (They’re carrying 50 A each.) How about at 10 cm?

What about currents perpendicular to each other? …

Fun example: Force/m?

Fun example: How much current do you need in the third wire so the net forces are zero?

Current Loop: up/out down/in Solenoids

Current LoopS: up/out down/in

Solenoid: up/out down/in

WRENCH DEMO

Example: What’s the B-field inside a coil with 50 turns/cm, running a current of 2 A?

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