A rectangular loop carrying a current i1, is situated near a long straight carrying a straight current i2. The wire is parallel to one of the sides of the loop as shown in the figure. Then the current loop will
move away from the wire
move towards the wire
remain stationary
rotate about axis parallel to wire
The maximum distance upto which TV transmission from a TV of height h can be received is proportional to
h1/2
h
h3
h2
In short wave communication, waves of which of the following frequencies will be reflected back by the ionospheric layer having electron density 1011 per m3 ?
2 MHz
10 MHz
12 MHz
18 MHz
Using mass (M), length (L), time (T ) and current (A) as fundamental quantities, the dimension of permeability is
[ M-1 L T-2 A ]
[ M L2 T-2 A-1 ]
[ M L T-2A-2 ]
[ M L T-1 A-1 ]
A laser beam is used for carrying out surgery because it
is highly monochromatic
is highly coherent
is highly directional
can be sharply focused
A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1 kV, its kinetic energy will be
1840 keV
1/1840 keV
1 keV
920 keV
To a germanium sample, traces of gallium are added as an impurity. The resultant sample would behave like
a conductor
a p-type semiconductor
an n-type semiconductor
an insulator
B.
a p-type semiconductor
An intrinsic germanium have four outer electrons which they use to form bonds with four neighbouring Ge atoms. Gallium, being from group ( III ) is having three outer electrons. So when we add gallium atoms into germanium, some gallium atoms have a chance to replace some of the germanium atoms. But with gallium, only three neighbouring Ge atoms can make bonds with Ga. The bond with the fourth neighbouring Ge atom is broken as Ga is having a shortage of one outer electron. The broken bond can be filled up by an electron when the electron gets enough energy to jump from the valence bond creating hole out there. So, we get a p-type semiconductor.
A radioactive substance decays to 1/16th of its initial activity in 40 days. The half-life of the radioactive substance expressed in days is
2.5
5
10
20
A neutron makes a head-on elastic collision with a stationary deuteron. The fractional energy loss of the neutron in the collision is
16/81
8/9
8/27
2/3
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is
polarised
of longer wavelength
of shorter wavelength
of high intensity