A Galvanometer is connected as shown in the figure: Derive an expression to find the value of resistance S .

In the given question we have to use the concept of Ohm;s law and apply it to solve the given question. We have by Ohms's law, V = I R Applying Ohm’s law in the given circuit, I g R g = I - I g S ⇒ S = I g R g I - I g Hence, the expression is correctly derived.

The temperature dependence of resistivity of a material is shown below: Identify the type of material.

In a semiconductor when temperature increases conductivity increases so resistivity decreases i.e. T ∝ ρ 1 ρT = constant ⇒ ρ = K 1 T dρ = − K 1 T 2 dT ⇒ dT dρ = − K T 2 So, slope of ρ−T curve is negative & it is dependent upon T i.e. it is not constant. Hence, the required material is semiconductor.

The temperature dependence of resistivity of a material is shown below: b Write the relation between resistivity and average collision time for electron.

The average of velocities of all electrons just after collisions is 0, as they get bounced in all random directions. Hence, the average velocity of an electron along the length of a resistor or conductor wire is equal to that gained due to electrostatic field E. So the required relation is v = eJρτ m ⇒ τ = mv eJρ .

The experimental set up to find an unknown resistance using a metre bridge is shown below: a What is the working principle for a metre bridge?

The principle of working of Metre bridge is wheat stone bridge principle and it is used to find the resistance of an unknown conductor or to compare two unknown resistance.

The experimental set up to find an unknown resistance using a metre bridge is shown below: If the galvanometer and cell are interchanged at the balance point of the bridge, would the galvanometer show any current?

A galvanometer is a device that detects or measures the magnitude of a tiny electric current. The movement of a magnetic needle or a coil in a magnetic field, which is an integral part of a galvanometer, is commonly used to indicate the current and its strength. Now, If the galvanometer and cell are interchanged at the balance point of the bridge.The balance point remains unaltered if the galvanometer and the cell are swapped. As a result, the galvanometer will display no current and the deflection will be zero.

The experimental set up to find an unknown resistance using a metre bridge is shown below: b If the balance point is found to be at 39 . 5 cm from the end A , the resistor S is of 12 . 5 Ω . Determine the resistance R . Why are the connections between resistors in a metre bridge made of thick copper strips?

Condition for balanced wheatstone bridge, X Y = 100 − l 1 l 1 Y = 12 . 5 Ω I 1 = 39 . 5 c m X = 8 . 2 Ω To minimize the resistance which is not taken into formula.

The experimental set up to find an unknown resistance using a metre bridge is shown below: a What is the working principle for a metre bridge?

The principle of working of Metre bridge is wheat stone bridge principle and it is used to find the resistance of an unknown conductor or to compare two unknown resistance.

The temperature dependence of resistivity of a material is shown below: b Write the relation between resistivity and average collision time for electron.

The average of velocities of all electrons just after collisions is 0, as they get bounced in all random directions. Hence, the average velocity of an electron along the length of a resistor or conductor wire is equal to that gained due to electrostatic field E. So the required relation is v = eJρτ m ⇒ τ = mv eJρ .

The temperature dependence of resistivity of a material is shown below: Identify the type of material.

In a semiconductor when temperature increases conductivity increases so resistivity decreases i.e. T ∝ ρ 1 ρT = constant ⇒ ρ = K 1 T dρ = − K 1 T 2 dT ⇒ dT dρ = − K T 2 So, slope of ρ−T curve is negative & it is dependent upon T i.e. it is not constant. Hence, the required material is semiconductor.

The transfer characteristic of n - p - n , transistor in CE - configuration is shown in the figure. In the working of a transistor, the emitter-base ( EB ) - junction is forward biased while collector base ( CB ) - junction is reverse biased. Why ?

This bias system is the condition of the transistor to be active. As the emitter-base is forward biased the input resistance i.e the resistance of the emitter-base junction becomes very small. Again as the collector base junction is reverse biased the output resistance i.e the resistance of the emitter-collector becomes very high. The circuit with low input resistance and high output resistance acts as the best amplifier. That is why the emitter-base junction is forward biased while collector-base junction is reversed biased.

The transfer characteristic of n - p - n - transistor in CE - configuration is shown in the figure. A CE - transistor amplifier is shown in figure. In this, the audio signal voltage across collector resistance of 2 . 0 KΩ is 2 . 0 V . Suppose the current amplification factor of the transistor is 100 . Then calculate the value of signal current through the base.

Given that, The audio signal voltage is V bb = 2 v , and the collector resistance is R c = 2 kΩ = 2000 Ω . Also, the current amplification factor is β = 100 . Therefore, I c = 2 2000 = 1 mA , and we know that β = I c I b . Where I c , is the collector current and I b , is the base current. ⇒ I b = I c β = 1 mA 100 = 10 - 5 A . Hence, This is the required answer.