ISRO Old Question Paper : Scientist / Engineer

Name of the Organisation : Indian Space Research Organisation (isro.gov.in)
Type of Announcement : Old Question Paper
Designation : Scientist / Engineer

Old Question Papers :
Civil : https://www.indianjobtalks.in/uploads/27063-civil-qp-2013.pdf
Electrical : https://www.indianjobtalks.in/uploads/27063-Electrical-qp-2013.pdf
Refrigeration & A/C : https://www.indianjobtalks.in/uploads/27063-Ref%20-%20AC-qp-2013.pdf
Home Page : http://www.isro.org/

Electrical Engineering —2013 SET A
1. The energy stored in the magnetic field in a solenoid of length 30cm and diameter 3cm wound with 1000 turns of wire & carrying a current of 10A is
a) 0.015 joules.
b) 0715 joules.
c) 0.5 joules.
d) 1.15 joules
2 . A network is said to be linear, if and only if
a) The response is proportional to the excitation function.
b) The principle of superposition applies.
c) The principle of homogeneity applies.
d) The principles of superposition and homogeneity apply.
3 . Kirchoff’s law fails in the case of
a) Non-linear networks.
b) Linear networks.
c) Dual networks.
d) Distributed parameter networks
4. In a four branch parallel circuit, 50mA current flows in each branch. If one of the branches opens, the current in other branches
a) Increase, but not double
. b) Decrease.
c) Unaffected.
d) Double.
5. The wave length of a wave in a waveguide is
a) is greater than in free space
b) depends only on the waveguide dimensions and the free-space Wavelength
c) is inversely proportional to the phase velocity
d) is directly proportional to the group velocity
6. Characteristic impedance of a quarter wave transformer connected in between a load of 100 ohm and a transmission line of characteristic impedance 225 ohms is
a) 100 ohm
b) 225 ohm
c) 600 ohm
d) 150 ohm
7. A transverse electromagnetic wave with circular polarization is received by a dipole antenna due to polarization mismatch. The power transfer efficiency from the wave to the antenna is reduced to about
a) 50%
b) 35.5%
c) 25%
d) 0%
8. The unit of displacement density of a magnetic circuit is
a) Coulomb / metre
b) Coulomb / sq. metre
0) Newton – cm
d) Amp / metre
9. The derivative of an ideal step function is
a) an impulse function
b) zero
c) sine function
d) undefined
10. An impulse function consists of
a) entire frequency range with same relative phase
b) infinite bandwidth with linear phase variation
0) pure DC
d) large DC with weak harmonics
11. The discrete time system described by y(n) = x(n2) is
a) causal, linear and time varying
b) causal, nonlinear and time varying
c) non-causal, linear and time invariant
d) non-causal, non linear and time variant
12. What does the transfer function of a system describe for the system?
a) only zero input response
b) only zero state response
c) both zero input and zero state response
d) neither zero input response nor zero state‘response

13. Which of the following measures cannot be effective in reducing the noise?
a) reduction in signaling rate
b) increase in transmitted power
c) increase in channel bandwidth
d) use of redundancy
14. Which among the following type of transformer have smallest size with same electrical specification ?
a) ONAN type transformer.
b) Dry type transformer.
c) ONAF type transformer.
d) OFWF type transformen
15. Two transformers operating in parallel will share the load depending upon their ?
a) Ratings.
b) Leakage reactance.
c) Efficiency.
d) Per unit impendence.
16. Transformer core is laminated,
a) because it is difficult to fabricate solid core.
b) because laminated core provides high flux density.
c) to avoid eddy current and hysteresis losses.
d) to increase the main flux.
17. The eddy current losses in the transformer will be reduced if ?
a) The lamiriations are thick.
b) Number of turns in the primary winding is reduéed.
c) The number of turns in the secondary winding is reduced.
d) The iaminations are thin.
18. The Buchholz relay is used to protect the ?
a) Alternators against all internal faults.
b) Oil immersed transformers against all internal faults.
c) Synchronous motors against all internal faults.
d) Transmission lines against all short circuit faults.
19. Why are transformer stamping annealed before being used for the building?
a) to reduce eddy-,current loss due to burning of edges
b) to reduce hysteresis loss due to burning of edges
c) to give mechanical strength to the core
d) to increase core permeability
20. As compared‘to A — A bank, the capacity of the V -V bank of transformers is —- percent.
21. A transformer on no-Ioad is switched on to a source of voltage; It will draw
a current —
a) which is the same as the steady-state magnetizing current
b) which is several times the steady-statemagnetizing current, depending upon , the initial state of the residual flux in the transformer core.
c) which is several times the steady-state magnetizing current, independent of the initial state of the residual flux in the transformer core.
d) which is twice the steady-state magnetizing current provided the core has no residual flux.
22. On the two sides of a star/delta transformer —
a) the voltage and current are both in phase
b) the voltage and current both differ in phase by 30°
c) the voltage differ in phase by 30° but currents are in phase
d) the current differ in phase by 30° but voltages are in phase.
23. In a Scott-connected transformer the number of primary and teaser turns respectively are —
24. The use of higher flux density in the transformer design —
a) decreases the total weight/ kVA
b) increases the total weight/ kVA
c) decreases the Weight of iron / kVA but increases that of copper
d) decreases the weight of copper / kVA but increases that of iron
25. The applied voltage of a certain transformer is increased by 50% while the frequency is reduced by 50%. The maximum core flux density will become —
a) three times
b) 1.5 times
c) 0.5 times
d) will remain the same.