GEHU Format For Doc No GEU/07/7.5Issue No-01/Rev No. 00Date of Issue: 01/02/2013

Assignment & Tutorial Sheet for Academic year

Page No. 1 of 1

Assisgnment& Tutorial Sheet for Academic Year 2014Faculty Name:-VAIBHAV AGARWAL

Course Code:-TEE- 302

Sem/Branch/Section:-III/EEE

Course Title:-ELECTRICAL AND ELECTRONICS ENGINEERING MATERIALS

Subject Code:-

Date of Submission:-

Assignment No:-02

Q1). In a certain copper conductor, the current density is 2.4 A/mm2 and electron density is 5x1028 free electrons per m3 of the copper. Determine the drift velocity of the electrons ?

Q2). A conductor material has a free electrons density of 1024 electrons per m3. When a voltage is applied, a constant drift velocity of 1.5x10-2 m/s is attained by the electrons. If the x-sectional area of the material is 1 cm2. Calculate the magnitude of the current. Electronic charge is 1.6x10-19coloumb ?

Q3). A conduction wire has a resistivity of 1.54x10-8Ω-m at room temperature. There are 5.8x1028 conduction electrons per m3. Calculate the mobility and relaxation time of electrons?

Q4). A conducting wire has a resistivity of 1.5x10-8 Ω-m at 300 K. Its Fermi energy is 5eV. Its volume of 1 m3 contains 6x1028 conducting electrons. Calculate the relaxation time of conducting electrons. Hence or otherwise obtain the value of drift velocity of electrons, when the conductor is subjected an electric field of 100 V/m. Write the significance of relaxation time and drift velocity.

Given: Mass of electrons =9.107 x 10-31 kg; Electron charge = 1.601 x 10-19 C.

Q5). A n-type germanium crystal has a current density of 100A/m2. The crystal has a resistivity of 0.5 Ω-m and electron mobility of 0.4 m2/V-s. Calculate the drift velocity and the time taken by the electron to travel 10 micro-m in the crystal. Assume e = 1.6 x 10-19 C.

Q6). A coil of copper wire has a resistance of 250 Ω at 150C. Find its temperature when its resistance is 300Ω.(for copper α= 0.00390C-1).

Q7). Show that if α1is the resistance temperature coefficient of a conductor at t 10 C then resistance temperature coefficient at t 20 C is given by:-

11α0

+(t 2−t 1)

Q8). Determine the temperature coefficient of resistance of material used in a resistor if the resistance at 250C is 45 ohm and at 750C is 59 ohms ?

Q9). A platinum coil has a resistance of 3.146Ω at 40oC and 3.767Ω at 1000C. Find the resistance at 00C and the temperature coefficients of resistance at 400C ?

Q10). Explain about the various thermoelectric effects with their neat and clean diagrams?

Last Date of Submission :-22/08/2014