### Eamcet - Physics - Current Electricity

A 6 V cell with 0.5 Ω  internal resistance, a 10 V cell with 1 Ω internal resistance and a 12 Ω external resistance are connected in parallel. The current (in ampere) through the 10 V cell is :

A.  0.60

B.  2.27

C.  2.87

D.  5.14

Consider the following statements A and B and identify the correct answers given below :A : Peltier coefficient is numerically equal to the potential difference across the junctions of the thermocouple through which current is flowing.B : According to Thomson, energy is neither absorbed nor evolved at the junction of a thermocouple but is observed or evolved only along the lengths of both the conductors.

A.  both A and B are true

B.  both A and B are false

C.  A is true but B is false

D.  A is false but B is true

Two cells A and B are connected in the secondary circuit of a potentiometer one at a time and the balancing length are respectively 400 cm and 440 cm. The emf of the cell A is 1.08 volt. The emf of the second cell B in volts is :

A.  1.08

B.  1.188

C.  11.88

D.  12.8

In a meter bridge a 30 Ω resistance is connected in the left gap and a pair of resistances P and Q in the right gap. Measured from the left, the balance point is 37.5 cm, when P and Q are in series and 71.4 cm when they are parallel. The values of P and Q (in Ω ) are

A.  40 10

B.  35 15

C.  30 20

D.  25 25

An aluminum (resistivity ρ = 2.2 x 10-8 Ω-m) wire of a diameter 1.4 mm is used to make a4Ω resistor. The length of the wire is

A.  220 m

B.  1000 m

C.  280 m

D.  1 m

In a metre bridge experiment, the ratio of the left gap resistance to right gap resistance is 2 : 3, the balance point from left is

A.  60

B.  50

C.  40

D.  20

Temperature of cold junction in a thermo- couple is 100C and neutral temperature is 2700C, then the temperature of inversion is

A.  540o C

B.  530o C

C.  280o C

D.  260o C

One end each of a resistance r capacitor C and resistance 2r are connected together. The other ends are respectively connected to the positive terminals of batteries, P, Q, R having respectively emfs E, E and 2E. The negative terminals of the batteries are then connected together. In this circuit, with steady current the potential drop across the capacitor is ;

A.  E/3

B.  E/2

C.  2E/3

D.  E

Twelve cells, each having emf E.volts are connected in series and are kept in a closed box. Some of these cells are wrongly connected with positive and negative terminals reversed. This 12 cell battery is connected in series with an ammeter, an external resistance R ohms and a two-cell battery (two cells of the same type used earlier, connected perfectly in series). The current in the circuit when the 12-cell battery and 2-cell battery aid each other is 3A and is 2A when they oppose each other. Then, the number of cells in 12-cell battery that are connected wrongly is :

A.  4

B.  3

C.  2

D.  1

If the cold junction is held at 00C, the same thermo emf V of a thermocouple varies as V = 10 x 10 6t - * x 10 bt2, where t is the 40 temperature of the hot junction in 0C. The neutral temperature and the maximum value of thermo emf are respectively:

A.  200oC ; 2 mV

B.  400oC ; 2 mV

C.  100oC ; 1 mV

D.  200oC ; 1 mV

A cell in secondary circuit gives null deflection for 2.5 m length of potentiometer having 10 m length of wire If the length of the potentiometer wire is increased by 1 m without changing the cell in the primary, the position of the null point now is

A.  3.5 m

B.  3 m

C.  2.75 m

D.  2 m

Resistances are connected in the two gaps of a meter bridge.The balance point is 20cm from the zero end.When a 15Ω resistor is connected in series with the smaller resistance then the null point shifts to 40cm.the smaller resistance is

A.  80Ω

B.  9Ω

C.  10Ω

D.  12Ω

If in a Wheatstone bridge the battery and Galvanometer are interchanged, the condition for balance

A.  Is disturbed

B.  Is not disturbed

C.  Depends on the internal resistance of the bridge

D.  Depends on the values of the resistances in the bridge.

(A): bending of a conducting wire effects electrical resistance (R): Resistance of a wire depends on resistivity of that material

A.  A is false but R is true

B.  A is true but R is false

C.  Both A & R true and R is not a correct explanation of A

D.  Both A & R are true and R is the correct explanation of A

S.I unit of electrical conductivity

A.  Ohm metre

B.  Siemen metre

C.  Siemen/metre

D.  Siemen

Thomson coefficient of a conductor is 10μVK. The two ends of it are kept at 500 C and 600 C respectively. Amount of heat absorbed by the conductor when a charge of 10 C flows through it, is:

A.  1000 J

B.  100 J

C.  100 mJ

D.  1 mJ

When a high resistance R is connected in series with a voltmeter of resistance G, the range of the voltmeter increases 5 times. Then G:R will be

A.  4:1

B.  1:2

C.  8:1

D.  1:4

A steady current is set up in a metallic wire of non-uniform cross-section. Then the drift velocity related the area of cross-section (A) as

A.  Vd is independent of

B.  Vd A2

C.  Vd A

D.  Vd A-1

Thomson coefficient of a conductor is 10μV/K.The two ends of it are kept at 500C and 600C respectively.Amount of heat absorbed by the conductor when a charge of 10C flows through it is

A.  1000J

B.  100J

C.  100 mJ

D.  1 mJ

A 25 watt,220 volt bulb and a 100 watt,220 volt bulb are connected in series across 440 volt line

A.  Both bulb will fuse

B.  None of the bulb will fuse

C.  Only 25 watt bulb will fuse

D.  Only 100 watt bulb will fuse

A voltameter has internal resistance r ohms and range V volts.The value of resistance used in series to convert it into a voltmeter of range 4V volts is

A.  r/3

B.  3r

C.  r/4

D.  4r

In Potentiometer experiment,the balancing length with a cell in the secondary circuit is found to be 480cm.when a resistor of 8 ohm is connected in parallel to the cell the balancing length is found to be 420cm.The internal resistance of the cell is

A.  1.14Ω

B.  2Ω

C.  4.12Ω

D.  56Ω

Three unequal resistors in parallel are equivalent to a resistance 1 ohm. If two of them are in the ratio 1:2and if no resistance value is fractional the largest of the three resistances in ohms is

A.  4

B.  6

C.  8

D.  12

One junction of thermo couple is at 00C and the other junction is heated .Maximum current in the thermo couple is observed when hot junction is at 2400C.The temperature of the hot junction at which the direction of current reverses is

A.  2400C

B.  4800C

C.  3600C

D.  1200C

A cell of emf 2V and negligible resistance is connected in series with a resistance of 5 ohm,and a potentiometer wire of resistance 10 ohm.what is the potential drop per cm if the length of the potentiometer wire is 10m.The emf of a cell which is balanced by 750cm long wire is

A.  (1/250)(V/cm),1V

B.  (1/1250)(V/cm),0.6V

C.  (1/750)(V/cm),1V

D.  (1/1500)(V/cm),0.5V

A galvanometer of resistance 100Ω gives full scale deflection with 5mA current.To convert it into a 5 volt range voltmeter,the value of resistance connected in series is

A.  1 mega ohm

B.  10000 ohm

C.  9999 ohm

D.  900ohm

Four bulbs each marked 40 W. 250 V are connected in series with 250 V source. The total power output is

A.  10 W

B.  40 W

C.  160 W

D.  320 W

An electrical meter of internal resistance 20Ω gives full scale deflection when one milliampere current flows through it.The maximum current that can be measured by using three resistors of resistance 12Ω each,in milliamperes is

A.  4

B.  6

C.  8

D.  10

Two wires of same material and same length have their resistances in the ratio 5:7.The ratio of the masses of the wires is

A.  5:7

B.  7:5

C.  3:4

D.  4:3

In a thermo couple the cold junction is at 300C.The temperature of inversion is found to be 5400C,Then the neutral temperature is

A.  2700C

B.  5100C

C.  2850C

D.  2400C