• Nature of Resistance Temperature-Resistance Relationship Ohm's Law, Energy and Power Kirchhoff's Law • • Maxwell's Mesh Analysis 1. The steel of the third rail of a railway system has a resistivity of 21.4 μ-cm. If its cross-sectional area is 8.2 in², calculate the resistance per mile of rail, neglecting the effect of joints between sections. (1 point) 2. An incandescent lamp has a tungsten filament whose resistance is 96 at its operating temperature of 2900°C. Calculate the filament resistance when the lamp is disconnected from the electric source, under which condition its temperature is 24°C. (Use do = 0.0045 02/°C for tungsten) (1 point) 3. For the circuit shown, find the following: 50 V 602 10 V 702 a. the value of resistor R. (1 point) b. the equivalent resistance with respect to the 50-V source. (1 point) 4. For the circuit shown, determine all the currents in each branch using Kirchhoff's Laws. (3 points) A 5V 2 В -ний C 4 6 VT ww F E 5. Use Maxwell's Mesh to find I, and VAB…

For items 8-9, refer to the problem below. Find all the currents flowing in every resistor, power dissipation in every resistor and the total power of the circuit shown at the right using... 8. Kirchhoff's Laws (5 pts) 9. Maxwell's Mesh Analysis (5 pts) A 8 V 10 V B + 20 Ω 3Ω 202 wwww C wwww 202 + 50 www 12 V

• Nature of Resistance Temperature-Resistance Relationship Ohm's Law, Energy and Power Kirchhoff's Law • Maxwell's Mesh Analysis 1. A coil of copper wire (p = 10.37 2-cmil/ft) has a length of 600 ft. What is the length of an aluminum conductor (p 17 cmil/ft), if its cross-sectional area and resistance are the same as those of the copper coil? (Hint: Look for conversion of inches to mils and square inches to square foot. Include it in your solution.) (1 pt) 2. The copper field winding of an electric machine has a resistance of 46 at temperature of 22°C. What will be its resistance at 75°C? (Use do = 0.00427 /°C for copper) (1 pt) 3. The resistivity of a copper rod 50 ft long and 0.25 inch in diameter is 1.76 μ at 20°C. What is its resistance at - 20°C? (1 pt) 4. When two resistors A and B are connected in series, the total resistance is 36 2. When connected in parallel, the total resistance is 8 Q. What is the ratio of the resistance RA to resistance RB? Assume RA < RB. (1 pt) 5. The…

2. Two equally strong individuals, wearing exactly the same shoes decide to do a tug of war. The only difference is individual A is 2.5 meters tall and individual B is 1.5 meter tall. Who is more likely to win the tug of war?

6. A car drives at steady speed around a perfectly circular track. (a) The car's acceleration is zero. (b) The net force on the car is zero. (c) Both the acceleration and net force on the car point outward. (d) Both the acceleration and net force on the car point inward. (e) If there is no friction, the acceleration is outward.

9. A spring has a force constant of 100 N/m and an unstretched length of 0.07 m. One end is attached to a post that is free to rotate in the center of a smooth. table, as shown in the top view in the figure below. The other end is attached to a 1kg disc moving in uniform circular motion on the table, which stretches the spring by 0.03 m. Friction is negligible. What is the centripetal force on the disc? Top View (a) 0.3 N (b) 3.0 N (c) 10 N (d) 300 N (e) 1000 N

4. A child has a ball on the end of a cord, and whirls the ball in a vertical circle. Assuming the speed of the ball is constant (an approximation), when would the tension in the cord be greatest? (a) At the top of the circle. (b) At the bottom of the circle. (c) A little after the bottom of the circle when the ball is climbing. (d) A little before the bottom of the circle when the ball is descending quickly. (e) Nowhere; the cord is pulled the same amount at all points.

3. In a rotating vertical cylinder (Rotor-ride) a rider finds herself pressed with her back to the rotating wall. Which is the correct free-body diagram for her? (a) (b) (c) (d) (e)

8. A roller coaster rounds the bottom of a circular loop at a nearly constant speed. At this point the net force on the coaster cart is (a) zero. (b) directed upward. (c) directed downward. (d) Cannot tell without knowing the exact speed.