Physics Answers

1. How would you expect the resistivity of a good insulator such as glass or polystyrene to vary with temperature?

2. A fuse is a device that is designed to break the circuit. It melts when the current exceeds its value. What

characteristics should the material have?

1. Find the current density and drift velocity of free electrons when the particles travel on a copper conductor with a

square cross-section of 1.0 mm on the side and carries a current of 40 A to a 5 hp electric meter and its density of

6.0 x 1028 electrons/m3

2. Suppose the resistance is 1.47 Ω at a temperature of 20°C. Find the resistance at 0 degree Celsius.

A projectile is fired at an angle 30 ° from gun that is 45 m above the flat ground, emerging from the gun with a speed of 250 m/s. (a) How long does the projectile remain in air? (b) At what horizontal distance from the firing ground does it strike the ground? (c) What is the velocity of the projectile when it hits the ground?

A circular copper waveguide has a radius of 0.4 cm and is filled with a dielectric material having 𝜀𝑟 = 1.5 and tan δ = 0.0002.

2.1.1. Identify the first four propagating modes and their cut-off frequencies.

2.1.2. For the dominant mode, calculate the attenuation due to dielectric loss and attenuation due to conductor loss at 20 GHz.

A circular copper waveguide has a radius of 0.4 cm and is filled with a dielectric material having 𝜀𝑟 = 1.5 and tan δ = 0.0002.

2.1.1. Identify the first four propagating modes and their cut-off frequencies.

2.1.2. For the dominant mode, calculate the attenuation due to dielectric loss and attenuation due to conductor loss at 20 GHz.

The velocity of car A is 8m/s when the two cars are moving in the same direction and 28m/s when the two cars are moving in opposite directions. Determine the velocity of each car

A wire having the diameter of 1.2 mm and resistively of 100 * 10 ^ - 1 * Omega * m at 0°C is connected. across a cell of emf

1.5 V and gives a current of 10 mA. Calculate the length of the wire.

A delivery van is travelling at a constant speed of 15ms^-1 when the driver sees a pedestrian crossing 50m ahead of him. He takes exactly 1 sec before he apploes the brakes as hard as he can. It takes 3 sec for him to stop.

Will the van be able to stop before he reaches the pedestrian crossing?

The diameter of 0---guage copper wire is 8.252 mm. Find the resistance of a 1.00-km length of such wire used for power transmission.

A 330-ohm resistor is connected to a 5-volt battery. The current through the resistor is?

Two circuits present the same resistance to the current. In one circuit the battery causing the flow of current has a voltage of 9.0 V, and the current is 3.0 A. In the other circuit the battery has a voltage of 1.5 V. What is the current in this other circuit?