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# Physics Homework

1. In the above figure, the ideal batteries have emfs ε1=10 V and ε2=0.5 ε1, and the resistances are each 4 Ω. What is the current in (a) resistance 2 and (b) resistance 3 ? 2. A 15 kΩ resistor and a capacitor are connected in series, and then a 12-V potential difference is suddenly applied across them. The potential difference across the capacitor rises to 5 V in 1.3 μs. (a) Calculate the time constant of the circuit. (b) Find the capacitance of the capacitor. 3. A horizontal power line carries a current of 5000 A from south to north. Earth’s magnetic field (60 μT) is directed toward the north and inclined downward at 70 ͦ to the horizontal. Find the (a) magnitude and (b) direction of the magnetic force on 100 m of the line due to Earth’s field. 4. An electron in an old-fashioned TV camera tube is moving at 7.2x106 m/s in a magnetic field of strength 83 mT. What is the (a) maximum and (b) minimum magnitude of the force acting on the electron due to the field ? (c) At one point the electron has an acceleration of magnitude 4.9x1014 m/s2. What is the angle between the electron’s velocity and the magnetic field ? 5. In the above figure, two long straight wires are perpendicular to the page and separated by a distance d1=0.75 cm. Wire 1 carries 6.5 A into the page. What are the (a)magnitude and (b) direction (into or out of the page) of the current in wire 2 if the net magnetic field due to the two currents is zero at point P located at distance d2 = 1.5 cm from wire 2 ? 6. The above figure shows a cross-section across a diameter of a long cylindrical conductor of radius a= 2 cm carrying a uniform current of 170 A. What is the magnitude of the current’s magnetic field at radial distance (a) 0, (b) 1 cm, (c) 2 cm (wire’s surface), and (d) 4 cm ? 7. In the above figure, a wire forms a closed circular loop, with radius R=2cm and resistance 4 Ω. The circle is centered on a long straight wire ; at time t=0, the current in the long straight wire is 5 A rightward. Thereafter, the current changes according to i= 5A-(2 A/s2) t2. (The straight wire is insulated; so there is no electrical contact between it and the wire of the loop.) What is the magnitude of the current induced in the loop at time t > 0 ? 8. A long solenoid has a diameter of 12 cm. When a current I exists in the windings , a uniform magnetic field of magnitude B=30 mT is produced in its interior. By decreasing i, the field is caused to decrease at the rate of 6.5 mT/s . Calculate the magnitude of the induced electric field (a) 2.2 cm and (b) 8.2 cm from the axis of the solenoid. 9. The current in an RL circuit drops from 1 A to 10 mA in the first second following removal of the battery from the circuit. If L is 10 H, find the resistance R in the circuit. 10. A coil is connected in series with a 10 kΩ resistor. An ideal 50 V battery is applied across the two devices, and the current reaches a value of 2 mA after 5 ms. (a) Find the inductance of the coil. (b) How much energy is stored in the coil at the same moment ? 11. Two coils are at fixed locations. When coil 1 has no current and the current in coil 2 increases at the rate 15 A/s, the emf in coil 1 is 25 mV. (a) What is their mutual inductance ? (b) When coil 2 has no current and coil 1 has a current of 3.6 A, what is the flux linkage in coil 2 ? 12. A coil with 150 turns has a magnetic flux of 50 mT-m2 through each turn when the current is 2 mA. (a) What is the inductance of the coil ? What are the (b) inductance and (c) flux through each turn when the current is increased to 4 mA ? (d) What is the maximum emf ɛ across the coil when the current through it is given by i=(3 mA) cos(377t), with t in seconds ?

Thanks for request. I will try to reply asap. It will be better if you can upload scan copy or word file of these questions.
Customer: replied 4 years ago.

How can I upload the word file on here? Please let me know asap

Upload the word file to some file sharing site such as media fire/wikisend. After this has been done, copy the site reference to this web page and it will allow me to view the word file.
Customer: replied 4 years ago.
Thanks. I have got the word file and will try to reply asap.
Customer: replied 4 years ago.

Ok no probelm. do you have an idea when will I be able to get the solutions for these problems?

Solving these questions will not take much time. Here it is 1.30AM now. I will reply these questions in morning, that is, in 8 hours or so.
Customer: replied 4 years ago.

Ok thanks a lot for your help. Please let me know if you will need any additional info from me! I am hoping to get the solutions within the next 12 hours or so.

Sure. I will reply by that time. I had a glimpse on the questions and hope there should not be any problem after I have got the word file. Still, if any, clarification is required, I will inform you. Thanks.
Customer: replied 4 years ago.
Hey I was wondering if you are done solving the questions?
I have solved all the problems except 7 where I have some doubt. I will upload the answers shortly.
Customer: replied 4 years ago.
Ok great thanks!