MCQ
In a $P$-type semi-conductor, germanium is dopped with
- AGallium
- BBoron
- CAluminium
- ✓All of these
✓
Answer
Correct option: D.
All of these
Gallium, boron and aluminum are trivalent.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A hospital uses an ultrasonic scanner to locate tumours in a tissue. The operating frequency of the scanner is $4.2 \mathrm{MHz}$. The speed of sound in a tissue is $1.7 \mathrm{~km}-\mathrm{s}$. The wavelength of sound in the tissue is close to
→A microammeter has a resistance of $100 \Omega$ and full scale range of $50 \mu \mathrm{A}$. It can be used as a voltmeter or as a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combination
→A body has a weight $90 \mathrm{~kg}$ on the earth's surface, the mass of the moon is $1 / 9$ that of the earth's mass and its radius is $1 / 2$ that of the earth's radius. On the moon the weight of the body is
→In a Carnot engine, when $T_2=0^{\circ} \mathrm{C}$ and $T_1=200^{\circ} \mathrm{C}$, its efficiency is $\eta_1$ and when $T_1=0{ }^{\circ} \mathrm{C}$ and $T_2=-200{ }^{\circ} \mathrm{C}$, its efficiency is $\eta_2$, then what is $\eta_1 / \eta_2$
→Unit of energy is
A source of sound emits waves with frequency $f \mathrm{~Hz}$ and speed $V$ $\mathrm{m} / \mathrm{sec}$. Two observers move away from this source in opposite directions each with a speed $0.2 \mathrm{~V}$ relative to the source. The ratio of frequencies heard by the two observers will be
→A body floats in a liquid contained in a beaker. If the whole system as shown in figure falls freely under gravity, then the upthrust on the body due to liquid is
The time period of a bar magnet suspended horizontally in the earth's magnetic field and allowed to oscillate
With the propagation of a longitudinal wave through a material medium, the quantities transmitted in the propagation direction are
A coil having an area $A_0$ is placed in a magnetic field which changes from $B_0$ to $4 B_0$ in a time interval $t$. The e.m.f. induced in the coil will be
→