Time left =
2
A capacitor of 10 pF is connected to a voltage source of 100 V. If the distance between the capacitor plates is reduced to 50%, while it remains connected to the 100 V supply, the value of potential gradient in the second case will be
3
An uncharged capacitor of 0.01 F is charged first by a current of 2 mA for 30 s and then by a current of 4 mA for 30 s. The final voltage in it will be
4
The magnetizing force at the centre of a circular coil varies
1. Directly as the number of its turns.
2. Directly as the current.
3. Directly as its radius.
4. Inversely as its radius.
Which of the above statements are correct?
5
A unit magnetic pole may be defined as that pole which when placed in vacuum at a distance of one metre from a similar and equal pole repels it with a force of
6
A point charge of 10–9 C is placed at a point A in the free space. The potential difference between the two points 20 cm and 10 cm away from the charge at A will be
7
Which of the following statements are correct?
1. A lowpass filter passes low frequencies and stops high frequencies.
2. A highpass filter passes high frequencies and rejects low frequencies.
3. A bandpass filter passes frequencies within a frequency band and attenuates frequencies outside the band.
4. A bandstop filter passes frequencies within the band and blocks/attenuates frequencies outside a frequency band.
8
Which of the following statements are correct for an ideal constant voltage source?
1. Its output voltage remains absolutely constant whatever the change in load current.
2. It possesses zero internal resistance so that internal voltage drop in the source is zero.
3. Output voltage provided by the source would remain constant irrespective of the amount of current drawn from it.
4. Output voltage provided by the source varies with the amount of current drawn from it.
9
For a network graph having its fundamental loop matrix Bf and its sub-matrices Bt and B l corresponding to twigs and links, which of the following statements are correct?
1. B l is always an identity matrix.
2. Bt is an identity matrix.
3. Bf has a rank of b – ( n – 1), where b is the number of branches and n is the number of nodes of the graph.
10
A voltage source-series resistance combination is equivalent to a current source-parallel resistance combination if and only if their
1. Respective open-circuit voltages are equal.
2. Respective short-circuit current are equal.
3. Resistance remains same in both cases.
Which of the above statements are correct
11
Which of the following statements is/are correct?
1. Conductor contain a large number of electrons in the conduction band at room temperature. No energy gaps exist and the valence and conduction bands overlap.
2. A semiconductor is a material in which the energy gap is so large that practically no electron can be given enough energy to jump this gap.
3. An insulator is a solid with an energy gap small enough for electrons to cross rather easily from the valence band to the conduction band
12
Light is capable of transferring electrons to the free-state inside a material thus increasing the electrical conductivity of the material. When the energy imparted to the electrons is quite large, the latter may be emitted from the material into the surrounding medium. This phenomenon is known as
13
The inductance of an air-cored coil is proportional to
1. The square of the number of turns.
2. The diameter of the coil.
3. A form factor, F, dependent on the ratio of coil radius to coil length plus winding depth. Which of the above statements are correct?
14
The magnetic moments of diamagnetic materials are mainly due to
15
If the interaction between the atomic permanent dipole moments is zero or negligible and the individual dipole moments are oriented at random, the material will be a
16
The paramagnetic susceptibility varies inversely with the absolute temperature for ordinary fields and temperatures. It is given by the relation χ =C TThe relation is known as
17
When ferromagnetic or ferrimagnetic materials are magnetized, the direction of magnetization in any domain will be rotated from its preferential direction. This will show an anisotropic behaviour. On removal of the magnetizing force, the total magnetization will in general have a non-zero value. This behaviour is due to
18
A transformer core is wound with a coil carrying an alternating current at a frequency of 50 Hz. The hysteresis loop has an area of 60000 units when the axes are drawn in units of 10–4 Wb m–2 and 102 Am–1. If the magnetization is uniform throughout the core volume of 0.01 m3, the power loss due to hysteresis will be