The cathode of a diode valve is replaced by another cathode of double the surface area. Keeping the voltage and temperature conditions the same, will the plate current decrease, increase or remain the same?

Two plates of equal areas are placed in contact wih each other. Their thickness are 2.0 cm and 5.0 cm respectively. The temperature of the external surface of the first plate is -20^(@)C and that of the external surface of the second plate is 20^(@)C . What will be the temperature of the current surface if the plates (i) are of the same material, (ii) have thermal conductivities in the ratio 2:5 .

If the radius of a cylinder is doubled keeping its lateral surface area the same, then what is its height ?

Two plates of equal areas are placed in contact with each other . Their thickness are 2 cm and 3 cm respectively. Temperature of the external surface of the first plate is -25^(@)C and that of the external surface of the second plate is 25^(@)C What will be temperature of contact surface if the plates:- (i) Are of same material (ii) Have thermal conductivity in ratio 2:3 .

A ring consisting of two parts ADB and ACB of same conductivity k carries an amount of heat H The ADB part is now replaced with another metal keeping the temperature T_91) and T_(2) constant The heat carried increases to 2H What should be the conductivity of the new ADB Given (ACB)/(ADB)=3 .

An experimental setup of verification of photoelectric effect is shown in the diagram. The voltage across the electrode is measured with the help of an ideal voltmetar, and which can be varied by moving jockey 'J' on the potentiometer wire. The battery used in potentiometer circuit is of 20 V and its internal resistance is 2omega . The resistance of 100 cm long potentiometer wire is 8 omega . The photo current is measured with the help of an ideal ammeter. Two plates of potassium oxide of area 50 cm^(2) at separation 0.5 mm are used in the vacuum tube. Photo current in the circuit is very small so we can treat potentiometer circuit an indepdent circuit. The wavelength of various colours is as follows : |{:("Light",underset("Violet")(1),underset("Blue")(2),underset("Green")(3),underset("Yellow")(4),underset("Orange")(5),underset("Red")(6)),(lambda "in" Årarr,4000-4500,4500-5000,5000-5500,5500-6000,6000-6500,6500-7000):}| The number of electrons appeared on the surface of the cathode plate, when the jockey is connected at the ened 'P' of the potentiometer wire. Assume that no radiation is falling on the plates.

An experimental setup of verification of photoelectric effect is shown in the diagram. The voltage across the electrode is measured with the help of an ideal voltmetar, and which can be varied by moving jockey 'J' on the potentiometer wire. The battery used in potentiometer circuit is of 20 V and its internal resistance is 2omega . The resistance of 100 cm long potentiometer wire is 8 omega . The photo current is measured with the help of an ideal ammeter. Two plates of potassium oxide of area 50 cm^(2) at separation 0.5 mm are used in the vacuum tube. Photo current in the circuit is very small so we can treat potentiometer circuit an indepdent circuit. The wavelength of various colours is as follows : |{:("Light",underset("Violet")(1),underset("Blue")(2),underset("Green")(3),underset("Yellow")(4),underset("Orange")(5),underset("Red")(6)),(lambda "in" Årarr,4000-4500,4500-5000,5000-5500,5500-6000,6000-6500,6500-7000):}| When radiation falls on the cathode plate a current of 2muA is recorded in the ammeter. Assuming that the vecuum tube setup follows ohm's law, the equivalent resistance of vacuum tube operating in this case when jockey is at end P.

Temperature of a conductor increases by 5^(@) C passing electric current for same time. The increase in its temperature when double current is passed through 1he same conductor the same time is ..... ""^(@)C .

A uniform wire of length l carrying current radiates energy at a rate P to environment while its temperature remains the same. Magnitude of magnetic flux density on the surface of wire is B and its diameter is d. If electric field strenght in wire is given by E=(nmu_(0)P)/(Bpild) , then find n.