AP Physics CHAPTER 18 WEEK 2 5/5 – 5/20

Homework and Test Schedule Review for AP test using Virtual Tutor 4/26-5/2 May 3 rd is AP test! Learn capacitors, magnetism, inductors 5/5-5/20 C20H1: Due 5/19 pg. 619 # 3, 4, 6, 13, 17, 22, 23, 45, 48, 51 Test 1 on 5/13 Quiz 2 on 5/18 Test 2 on 5/23 Review for Final 5/24-5/26 Q4RQ 5/31 Go over Q4RQ after school if desired Take Final 6/1 Graduate

22.If R=1 kΩ, and ε=250V, determine the direction and magnitude of the current in the horizontal wire between a and e. Circuits Practice I=50A flowing from a to e

24.Find the current in each resistor Circuits Practice I1=0.353A I2=0.118A I3=0.471A

25.What is the emf of the batter? Circuits Practice 10.67V

23.Determine a.The current b.The potential of wire A relative to ground c.The voltage drop across the 1500Ω resistor. Circuits Practice I=.003A V A =-19V V=4.5V

19.Four resistors are connected to a battery with a terminal voltage of 12V. Determine the power lost in the 50Ω resistor. Circuits Practice P=.52W

40.Three 2 ohm resistors are connected as shown. Each can dissipate a max on 32W without overheating. Determine the max power that the network can dissipate. Circuits Practice P=48W

27.Determine the potential difference, V ab, for the circuit. Note that each battery has an internal resistance as indicated. Circuits Practice V ab =9V

9.Determine the current through the 6, 18, and 9 ohm resistors Circuits Practice

26.Determine the potential difference, V ab, for the circuit. Circuits Practice I=.2A V ab =5.4V

61.What are the expected readings from the ammeter and the voltmeter shown? Circuits Practice V=1.5V I=.39A

55.Calculate a.The equivalent resistance b.Total power dissipated c.The current in the 5 ohm resistor Circuits Practice a. 14 ohms b. 56W c. 2A

Magnetism comes from the moving electrons within atoms. Most of the time the magnetism of the different electrons and atoms are so varied in direction that they effectively cancel each other out. Some materials naturally occur with magnetism and some materials can be made to have magnetism by being exposed to a magnet and/or force/friction. Magnetism Notes

Magnetism in the Earth comes from the charged moving/swirling liquid iron in the outer core. This is current which creates a magnetic field. The north pole of a magnet is attracted to the earth’s north pole. (north seeking) Like ends repel, opposite attract. Magnetic Field of the Earth is 5E-5 Teslas Magnetism Notes

Magnetic fields affect moving charges and moving charges produce magnetic fields. The ultimate sources of all magnetic fields is electric current, whether it be the current in a wire or the current produced by the motion of charges within atoms or molecules. Forces between magnetic poles are different from forces between electric charges because no matter how many times a permanent magnet is cut, each piece always has a north and a south pole, AKA, magnetic poles are always in pairs as opposed to electric charges. Magnetism Notes

Magnetic force is max value when the magnetic field and charge particle move perpendicularly to each other. The force is 0 when the particle moves along the field lines. What are the units? Magnetism Notes

Conventional current direction follows the “positive holes” Conventional current direction is the same as velocity of a positively charged particle so keep using right hand rule, not left hand. Magnetism Notes

Right hand rule Current, I, through a wire produces a magnetic field, B. The force on the wire from an outside field, B and current, I. Current / Negatives! Magnetic Field Force

14.A wire carries a current of 10A in a direction that makes an angle of 30 with the direction of a magnetic field of strength 0.3T. Find the magnetic force on a 5m length of the wire. Magnetism Practice 7.5N

16.A current of 15A is directed along the positive x-axis and perpendicularly to a magnetic field. The conductor experiences a magnetic force per unit length of 0.12N/m in the negative y- direction. Calculate the magnitude and direction of the magnetic field in the region through which the current passes. Magnetism Practice 8E-3 T out of the page

18.Find the direction of the magnetic field. Magnetism Practice a) Into b) right c) down

19.A wire with a mass of 1g/cm is placed on a horizontal surface with a coefficient of friction of 0.2. The wire carries a current of 1.5A eastward and moves horizontally northward. What are the magnitude and direction of the smallest magnetic field that enables the wire to move in this fashion? Magnetism Practice 0.131T

21.A thin 1m long copper rod has a mass of 50g. What is the minimum current in the rod that will cause it to float in a magnetic field of 2T? Magnetism Practice.245A

20.A uniform horizontal wire with a linear mass density of 0.5g/m carries a 2A current. It is placed in a constant magnetic field with a strength of 4E-3 T that is perpendicular to the wire. As the wire moves upward starting from rest what is the acceleration of the wire? Magnetism Practice 6.2 m/s 2

46.At what distance from a long straight wire carrying a current of 5A is the magnetic field due to the wire equal to the strength of the Earth’s field? 47.Niobium metal becomes a superconductor (with zero electrical resistance) when cooled below 9K. If superconductivity is destroyed when the surface magnetic field exceeds 0.1T, determine the maximum current a 2mm diameter niobium wire can carry while remaining a superconductor. Magnetism Practice 2 cm 500A