Assignment:
Q1. A beam contains 2.0 x 108 doubly charged positive ions per cubic centimeter, all of which are moving north with a speed of 1.0 x 105 m/s. What are the (a) njgnitude and (b) direction of the current density J? (c) What additional quantity do you need to calculate the total current i in this ion beam?
Q2. A 120 V potential difference is applied to a space heater whose resistance is 14 Ω when hot.
(a) At what rate is electrical energy transferred to thermal energy?
(b) What is the cost for 5.0 h at US$ξ0.05/k(W- h?
Q3.(a) At what temperature would the resistance of a copper conductor be double its resistance at 20.0°C?
(b) Does this same "doubling temperature" hold for all copper conductors, regardless of shape or size?
Q4. In Fig, the ideal batteries have emfs ξ1, = 12 V and ξ = 6.0 V. What are (a) the current, the dissipation rate in (b) resistor 1 (4.0 Ω) and (c) resistor 2 (8.0 Ω), and the energy transfer rate in (d) battery 1 and (e) battery 2? Is energy being supplied or absorbed by (f) battery I and (g) battery 2?
Q5. A total resistance of 3.00 Ω is to be produced by connecting an unknown resistance to a 12.0 Ω resistance.
(a) What must be the value of the unknown resistance, and
(b) should it be connected in series or in parallel?
Q6. A capacitor with initial charge qo is discharged through a resistor. What multiple of the time constant r gives the time the capacitor takes to lose (a) the first one-third of its charge and (b) two-thirds of its charge?
Q7. A proton traveling at 23.0° with respect to the direction of a magnetic field of strength 2.60 mT' experiences a magnetic force of 6.50 x I0-17 N. Calculate (a) the proton's speed and (b) its kinetic energy in electron-volts.
Q8. An electron that has velocity v: = (2.0 x 106 m/s)j + (3.0 x 106 m/s)j moves through the uniform magnetic field B= (0.030 T)j - (0.15 T) j.
(a) Find the force on the electron due to the magnetic field.
(b) Repeat your calculation for a proton having the same velocity.