The temperature dependence of resistances of Cu and undoped Si in the temperature range 300-400 K is best described by:
Linear increase for Cu, linear increase for Si.
Linear increase for Cu, exponential increase for Si.
Linear increase for Cu, exponential decrease for Si.
Linear decrease for Cu, linear decrease for Si.
C.
Linear increase for Cu, exponential decrease for Si.
As we know Cu is a conductor, so increase in temperature, resistance will increase. Then, Si is a semiconductor, so with the increase in temperature, resistance will decrease.
A p–n junction (D) shown in the figure can act as a rectifier. An alternating current source (V) is connected in the circuit.
C.
Only +ve current passes though the diode. Given figure is half wave rectifier.
The I-V characteristic of an LED is
A.
For same value of current, higher value of voltage is required for higher frequency.
Identify the semiconductor devices whose characteristics are given below, in the order (a), (b), (c), (d):
A.
Zener diode works in breakdown region
So, simple diode → (a)
zener diode (b)
solar cell → (c)
Light dependent resistance → (d)
The combination of gates shown below yields
OR gate
NOT gate
XOR gate
NAND gate
A.
OR gate
A | B | X |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 1 |
In a common emitter amplifier circuit using an n-p-n transistor, the phase difference between the input and the output voltages will be
135°
180°
45°
90°
B.
180°
In common emitter amplifier circuit input and output voltage are out of phase. When the input voltage is increased then i_{b} is increased, i_{c} also increases so the voltage drop across R_{c} is increased. However, increase in voltage across R_{C} is in opposite sense.
A charge Q is uniformly distributed over the surface of non conducting disc of radius R. The disc rotates about an axis perpendicular to its plane and passing through its centre with an angular velocity ω. As a result of this rotation, a magnetic field of induction B is obtained at the centre of the disc. If we keep both the amount of charge placed on the disc and its angular velocity to be constant and vary the radius of the disc than the variation of the magnetic induction at the centre of the disc will be represented by the figure
A.
Consider ring like the element of the disc of radius r and thickness dr.
If σ is charge per unit area, then charge on the element
dq = σ(2πr dr)
current ‘i’ associated with rotating charge dq is
Magnetic field dB at center due to element
So if Q and w are unchanged then
If a, b, c, d are inputs to a gate and x is its output, then, as per the following time graph, the gate is:
NOT
AND
OR
NAND
C.
OR
The output of OR gate is 0 when all inputs are 0 and output is 1 when at least one of the input is 1.
Observing output x it is 0 when all inputs are 0 and it is 1 when at least one of the inputs is 1.
therefore, the gate is OR