current electricity

Question 1

the phase between drift velocity/steady current and electric fiel or potential

Answer 1

pi
180 degrees

Question 2

Ohm’s law can be applied to

1. A. A.C
2. B. D.C

Answer 2

both

Question 3

The specific resistance of a conductor increases with:

Answer 3

Increase in temperature
Because specific resistance is independent of dimensions of a wire.

Question 4

The resistance of a wire is 11 Ohm. Its length is increased by 10% stretching. The new resistance will be

Answer 4

2n + n2/100 ; n=10%
210% + (1010/100)
20 + 1 = 21 %
11 + 0.21 -> 11.2

Question 5

The slope of current-voltage graph gives us:

Answer 5

Conductance
1/R

Question 6

The deviation of I-V graph from the straight line is due to

Answer 6

increase in temp and increase in R

Question 7

what is the practical unit of power

Answer 7

horse power

Question 8

what is the cgs unit of power

Answer 8

Erf sec-1

Question 9

Under what condition is the e.m.f. of a cell equal to its terminal voltage?

Answer 9

when no current is drawn from cell
The potential difference between the terminals of a battery will equal the emf of the battery when there is no current in the battery. At this time, the potential drop across the internal resistance is zero. This only happens when there is no load placed on the battery that includes measuring the potential difference with a voltmeter. The terminal voltage will exceed the emf of the battery when current is driven backward through the battery, in at its positive terminal and out at its negative terminal.

Question 10

Heat produced by current I in the wire of resistance R is?

Answer 10

Power = I2​R. To convert power to energy we need to multiply it with time. So heat produced (energy) = I2​Rt.

Question 11

Two electric bulbs rated P1 watt V volts, and P2 watt V volts are connected in series and applied across V volts. The total power will be

Answer 11

Power will be (p1 + p2) watt when connected in parallel and P1P2 / (P1 + P2) when connected in series.

Question 12

Increase in the temperature for a substance results in?

Answer 12

Resistance may increase or decrease with the increase in temperature. For conductors it increase and for semi-conductors and insulators it decreases.

Question 13

The potential difference between the terminals of battery in open circuit is 2.2 V. When it is connected across a resistance of 5.0 ohm, the potential falls to 1.8 V. What is the current of the battery?

Answer 13

when you draw current from a battery, the terminal voltage decreases. For example: when you start your car with the headlights on, they dim while you’re cranking the engine. This is why the model for a battery is an ideal voltage source (voltage constant regardless of output current) in series with the “internal resistance Ri “. Thus, the “open circuit voltage = 2.2V is the value of the ideal voltage source upstream from Ri. When you connect 5Ω across the terminals and read 1.8V you know the current in the 5Ω is
I = V/R = 1.8V/5Ω = 0.36A
Therefore that 0.36A Ri must be the cause of the voltage drop from 2.2V to 1.8V
=2.2-1.8 = 0.4V
0.4V = 0.36 × Ri
Ri = 0.4/0.36 = 40/36 = 10/9 Ω = 1.11111…..Ω

Question 14

For a metallic wire, the ratio of voltage to corresponding current is?

Answer 14

For a metallic wire with increase in temperature the resistance of the wire increases hence the ratio of voltage to corresponding current increases with rise in temperature

Question 15

E is EMF of a battery. What will be the potential drop across terminals an external resistance R = r (internal resistance) is connected across it?

Answer 15

E = Ir + Ir
of r = R
E = 2IR
E = 2V
V = E/2

Question 16

Internal resistances is the resistance offered by

Answer 16

electrolyte
The resistance is due to electrolyte present between the two electrodes of the cell is called the internal resistance of cell.

Question 17

The maximum output delivered to a load resistance is

Answer 17

E2 / 4r

Question 18

Which one is used to determine the internal resistance of the cell

Answer 18

Potentiometer can be used as:
i. Potential divider
ii. To measure the unknown EMF of the cell
iii. To compare the unknown EMFs of two cells
iv. To measure the internal resistance of cell

Question 19

Identify the type of application where heating effect of current is used:

Answer 19

when an electric current is passed through a conductor, it generates heat due to the hindrance caused by the conductor to the flowing current. The work done in overcoming the hindrance to the current generates heat in that conductor.
The heating effect of electric current is used in the following applications:
Electric Bulb: In an electric bulb, the filament of bulb gives light because of heating effect of electricity. The filament of bulb is generally made of tungsten metal; having melting point equal to 3380°C.
Electric iron: The element of electric iron is made of alloys having high melting point. Electric heater and geyser work on the same mechanism.
Electric fuse: Electric fuse is used to protect the electric appliances from high voltage; if any. Electric fuse is made of metal or alloy of metals, such as aluminium, copper, iron, lead, etc. In the case of flow of higher voltage than specified, fuse wire melts and protects the electric appliances.

Question 20

An electric iron is marked 20 volts 500 W. The units consumed by it in using it for 24 hours will be

Answer 20

12 kwH
500 * 24/1000

Question 21

Potentiometer practically draws

Answer 21

you can’t measure current by using potentiometer because potentiometer draws zero current under balanced condition. When the potentiometer is used in the circuit for measurement then it doesn’t draw any current. It can only be used to find either the internal resistance of a cell or the ratio of the emf (potential difference) of the two cells.

Question 22

Resistance of a super conductor is

Answer 22

Superconductors are materials that carry electrical current with exactly zero electrical resistance. This means you can move electrons through it without losing any energy to heat.

Question 23

The electrical analogue of mass in electricity is:

Answer 23

As per mechanical-electrical analog, displacement is analogous to charge and force analogous to voltage.
It can be concluded that electrical analog of mass is inductance.

Question 24

The resistance of a conductor at an absolute zero is

Answer 24

0

Question 25

Thermocouples generates energy at the cost of

Answer 25

heat energy
A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature.

Question 26

Temperature coefficient of thermistors

Answer 26

negative
hermistors with high negative temperature coefficient are very accurate for measuring low temperature especially near 10K.

Question 27

the change in a resistance of metallic conductor below 0?

Answer 27

linear

Question 28

formula for power dissipated in cables

Answer 28

P = I^2 R