Question
When the base current in a transistor is changed from $30\mu\text{A}$ to $80\mu\text{A},$ the collector current is changed from 1.0mA to 3.5mA. Find the current gain $\beta.$
✓
Answer
$\delta\text{I}_\text{b}=80\mu\text{A}-30\mu\text{A}=50\mu\text{A}=50\times10^{-6}\text{A}$
$\delta\text{I}_\text{c}=3.5\text{mA}-1\text{mA}$ $=-2.5\text{mA}=2.5\times10^{-3}\text{A}$
$\beta=\Big(\frac{\delta\text{I}_\text{c}}{\delta\text{I}_\text{b}}\Big)\text{V}_\text{ce}$ = constant
$\Rightarrow\frac{2.5\times10^{-3}}{50\times10^{-6}}=\frac{2500}{50}=50$
Current gain = 50.
$\delta\text{I}_\text{c}=3.5\text{mA}-1\text{mA}$ $=-2.5\text{mA}=2.5\times10^{-3}\text{A}$
$\beta=\Big(\frac{\delta\text{I}_\text{c}}{\delta\text{I}_\text{b}}\Big)\text{V}_\text{ce}$ = constant
$\Rightarrow\frac{2.5\times10^{-3}}{50\times10^{-6}}=\frac{2500}{50}=50$
Current gain = 50.
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 uniform slab of dimension $10\ cm \times 10\ cm \times 1\ cm$ is kept between two heat reservoirs at temperatures $10^\circ C$ and $90^\circ C.$ The larger surface areas touch the reservoirs. The thermal conductivity of the material is $0.80\text{wm}^{-1}{^{\circ}}\text{C}^{-1}.$ Find the amount of heat flowing through the slab per minute.
→From molecular view point, discuss the temperature dependence of susceptibility for diamagnetism, paramagnetism and ferromagnetism.
The. wire ABC shown in figure forms an equilateral triangle. Find the magnetic field B at the centre O of the triangle assuming the wire to be uniform.
In the relation to the photoelectric effect, write the definition of the terms 'stopping potential' and 'threshold frequency'. How are these physical quantities determined using Einstein's equation?
- Describe briefly the functions of the three segments of $\text{n-p-n}$ transistor.
- Draw the circuit arrangement for studying the output characteristics of $\text{n-p-n}$ transistor in $CE$ configuration. Explain how the output characteristics is obtained.
A traffic policeman sounds a whistle to stop a car$-$driver approaching towards him. The car$-$driver does not stop and takes the plea in court that because of the Doppler shift, the frequency of the whistle reaching him might have gone beyond the audible limit of $20 \text{kHz}$ and he did not hear it. Experiments showed that the whistle emits a sound with frequency close to $16 \text{kHz}.$ Assuming that the claim of the driver is true, how fast was he driving the car? Take the speed of sound in air to be 3$30m/s.$ Is this speed practical with today's technology?
→A vessel contains water upto a height of 20cm and above it an oil upto another 20cm. The refractive indices of the water and the oil are 1.33 and 1.30 respectively. Find the apparent depth of the vessel when viewed from above.
A resistor of $200 \Omega$ and a capacitor of $15.0 \mu F$ are connected in series to a $220 V , 50 Hz$ ac source.$ (a)$ Calculate the current in the circuit; $(b) $ Calculate the voltage $(rms)$ across the resistor and the capacitor. Is the algebraic sum of these voltages more than the source voltage? If yes, resolve the paradox.
→A rectangular wire frame, shown below, is placed in a uniform magnetic field directed upward and normal to the plane of the paper. The part AB is connected to a spring. The spring is stretched and released when the wire AB has come to the position A′ B′ (t = 0) How would the induced emf vary with time? Neglect damping.
Figure shows two blocks of masses m and M connected by a string passing over a pulley. The horizontal table over which the mass m slides is smooth. The pulley has a radius r and moment of inertia I about its axis and it can freely rotate about this axis. Find the acceleration of the mass M assuming that the string does not slip on the pulley.
