Week 71 A 1500W hairdryer is plugged into an electrical socket at your house (120V). What’s the current flowing through the hairdryer?

Week 72

3

4 Initially, the switch is open and the capacitor is uncharged. When the switch is closed current flows. Does the current 1) Increase with time? 2) Decrease with time? 3) Stay constant? 4) Increase and then decrease? 3

Week 75 The capacitor in the circuit below is initially uncharged. The switch is flipped to position ‘a’ at t=0. What current flows through the 50Ω resistor initially? What current flows through the 125Ω resistor initially? What current flows through the 125Ω after a long time?

Week 76 After the capacitor is fully charged, the switch is flipped to position ‘b’. What current flows through the 50Ω resistor initially? What current flows through the 50Ω resistor after a long time? Sketch a graph of the charge on and current through the capacitor vs time.

Week 77

8 Ferromagnetism

Week 79 Typical MRI 3 Highest magnetic fields 33 (continuous) created on Earth 66 (pulsed) Magnetars - a form of neutron star 10 11

Week 710

Week 711

Week 712

Week 713

Week 714 Does the compass needle rotate 1. clockwise, 2. counterclockwise or 3. not at all?

Week 715

Week 716 A positively charged particle moves towards the bottom of the screen. 1.At each of the six labeled points show the direction of the magnetic field or, if appropriate, write B=0. 2.Rank the positions in order from strongest to weakest magnetic field strength. Explain your reasoning.

Week 717 A positively charged particle is moving right at you from out of the screen. Draw magnetic field vectors at each position shown.

Week 718 How does your answer change if the charge coming at you is negative instead of positive?

Week 719 A proton moves along the x-axis with v x = 10 7 m/s. When it passes the origin what’s B at a - (1mm, 0, 0) ? b - (0, 1mm, 0) ? c - (1mm, 1mm, 0) ?

Week 720

Week 721 Two long, straight wires carry equal currents into and out of the screen. At each dot, draw and label the magnetic fields B 1 and B 2 of each wire. Then draw and label the net magnetic field, B net.

Week 722 Two long, straight wires carry equal currents out of the screen. a. At the position shown, draw and label the magnetic fields B 1 and B 2 of each wire. Then draw and label the net magnetic field, B net. b. Both wires are carrying currents of 10 Amps. Find the magnitude of B 1. c. Now find B net. Express your answer as a vector.

Week 723