Physics M.C.Q (1 Marks)

Assertion : Electric appliances with metallic body; e.g. heaters, presses etc, have three pin connections, whereas an electric bulb has a two pin connection.
Reason : Three pin connections reduce heating of connecting cables.

Assertion : Heat is generated continuously is an electric heater but its temperature becomes constant after some time.
Reason : At the stage when heat produced in heater is equal to the heat dissipated to its surrounding the temperature of heater becomes constant.

Assertion : The presence of water molecules makes separation of ions easier in electrolyte.
Reason : The presence of water molecules in electrolyte decreases the resistance of electrolyte.

Assertion : In all conductors, for studying the thermoelectric behaviour or metals, lead is taken as a reference metal.
Reason : In lead, the Thomson effect is negative.

Assertion : A domestic electrical appliance, working on a three pin will continue working even if the top pin is removed.
Reason : The third pin is used only as a safety device.

Assertion : A laser beam 0.2 W power can drill holes through a metal sheet, whereas 1000 W torch-light cannot.
Reason : The frequency of laser light is much higher then that of torch light.

Three wires of copper, iron and nickel are joined to form three junctions as shown in Fig. When the temperature of junction 1 is kept 50℃ with the other two junctions at 0℃, the sensitive galvanometer gives a deflection of 14 divisions. When the temperature of junction 3 is kept 50℃, with the other two junctions at 0℃, the galvanometer gives a deflection of 11 divisions. Then the deflection given by the galvanometer, when temperature of the junction 2 is kept at 50℃, with the other two junctions at 0℃, will be

A thermo couple uses Bismuth and Tellurium as the dissimilar metals. The sensitivity of bismuth is -72μV/℃ and that of the tellurium is 500μV/℃. If the difference between hot and cold junction is 100℃ then the maximum output will be

Assertion : If three identical bulbs are connected in series as shown in figure then on closing the switches. Bulb C short circuited and hence illumination of bulbs A and B decreases.






Reason : Voltage on A and B decreases

Assertion : In the given circuit if lamp B or C fuses then light emitted by lamp A decreases.







Reason : Voltage on A decreases. 

Assertion : Leclanche cell is used, when constant supply of electric current is not required.
Reason : The e.m.f. of a Leclanche cell falls, if it is used continuously.

Assertion : In practical application, power rating of resistance is not important.
Reason : Property of resistance remain same even at high temperature.

Assertion : Neutral temperature of a thermocouple does not depend upon temperature of cold junction.
Reason : Its value is constant for the given metals of the couple.

Assertion : Through the same current flows through the line wires and the filament of the bulb but heat produced in the filament is much higher then that in line wires.
Reason : The filament of bulbs is made of a material of high resistance and high melting point.

Assertion : Current is passed through a metallic wire, heating it red. When cold water is poured on half of its portion, then rest of the half portion become more hot.
Reason : Resistances decreases due to decrease in temperature and so current through wire increases.

Assertion : The possibility of an electric bulb fusing is higher at the time of switching ON and OFF
Reason : Inductive effects produce a surge at the time of switch ON and OFF

Assertion : The 200 W bulbs glows with more brightness then 100 W bulbs.
Reason : A 100 W bulb has more resistance than a 200 W bulb.

Assertion : Fuse wire must have high resistance and low melting point.
Reason : Fuse is used for small current flow only.

Assertion : Two electric bulbs of 50 and 100 W are given. When connected in series 50 W bulb glows more but when connected parallel 100 W bulb glows more.
Reason : In series combination, power is directly proportional to the resistance of circuit. But in parallel combination, power is inversely proportional to the resistance of the circuit.

In a copper voltameter, mass deposited in 30 second is m gm. If the time-current graph is as shown in figure, ECE of copper is]

Two different metals are joined end to end. One end is kept at constant temperature and the other end is heated to a very high temperature. The graph depicting the thermo e.m.f. is

Which of the following graphs shows the variation of thermoelectric power with temperature difference between hot and cold junction in thermocouples

A constant current i is passed through a resistor. Taking the temperature coefficient of resistance into account, indicate which of the plots shown in figure best represents the rate of production of thermal energy in the resistor

In a copper voltameter, mass deposited in 6 minutes is m gram. If the current-time graph for the voltameter is as shown here, then the E.C.E of the copper is

In a Ag voltameter 2.68 gm of silver is deposited in 10 min. The heat developed in 20Ω resistor during the same period will be

The wiring of a house has resistance 6Ω A 100 W bulb is glowing. If a geyser of 1000 W is switched on, the change in potential drop across the bulb is nearly

A silver voltameter of resistance 2 ohm and a 3 ohm resistor are connected in series across a cell. If a resistance of 2 ohm is connected in parallel with the voltameter, then the rate of deposition of silver

The same mass of copper is drawn into two wires 1 mm and 2 mm thick. Two wires are connected in series and current is passed through them. Heat produced in the wire is in the ratio

Four identical electrical lamps are labelled 1.5V, 0.5A which describes the condition necessary for them to operate at normal brightness. A 12V battery of negligible internal resistance is connected to lamps as shown, then

n immersion heater is rated 836 watt. It should heat 1 litre of water from 10℃ to 40℃ in about

In the circuit shown in figure, the heat produced in 5 ohm resistance is 10 calories per second. The heat produced in 4 resistance is

A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse. The maximum number of 60 W lamps in parallel that can be turned on, is

A coil of wire of resistance 50Ω is embedded in a block of ice. If a potential difference of 210 V is applied across the coil, the amount of ice melted per second will be

A thermocouple of resistance 1.6Ω is connected in series with a galvanometer of 8Ω resistance. The thermocouple develops and e.m.f. of 10 μV per degree temperature difference between two junctions. When one junction is kept at 0℃ and the other in a molten metal, the galvanometer reads 8 millivolt. The temperature of molten metal, when e.m.f. varies linearly with temperature difference, will be

Assertion : Two bulbs of same wattage, one having a carbon filament and the other having a metallic filament are connected in series. Metallic bulbs will glow more brightly than carbon filament bulb.
Reason : Carbon is a semiconductor.

Resistance of a voltameter is 2Ω, it is connected in series to a battery of 10 V through a resistance of 3Ω. In a certain time mass deposited on cathode is 1 gm. Now the voltameter and the 3Ω resistance are connected in parallel with the battery. Increase in the deposited mass on cathode in the same time will be

Which of the following plots may represent the thermal energy produced in a resistor in a given time as a function of the electric current

Peltier co-efficient of a thermo couple is 2 nano volts. How much heat is developed at a junction if 2.5 amp current flows for 2 minute

A thermo couple is formed by two metals X and Y metal X comes earlier to Y in Seebeck series. If temperature of hot junction increases beyond the temperature of inversion. Then direction of current in thermocouple will so

The V-i graphs A and B drawn for two voltameters. Identify each graph

A thermo couple develops 200μV between 0℃ and 100℃. If it develops 64μV and 76μV respectively between (0℃ - 32℃) and (32℃ - 70℃) then what will be the thermo emf it develops between 70℃ and 100℃

An electric bulb rated for 500 watts at 100 volts is used in a circuit having a 200-volt supply. The resistance R that must be put in series with the bulb, so that the bulb draws 500 W is