Current Electricity Questions and Answers

A wire when connected to 220 V mains supply has power dissipation P Now the wire is cut into two equal pieces which are connected in parallel to the same supply Power dissipation in this case is P Then P P is a 1 b 2 c 3 10 d 4

Q 102 In the circuit shown in the figure the power dissipated in the circuit is Po if an ideal cell is connected across A and B Same power is dissipated in the circuit if the same cell is connected across C and D When the cell was connected across A and D or across B and C the power dissipated in the circuit is found to be 3P Calculate the power dissipated in the circuit if the cell is connected across A and C VV A ww D

In the given circuit calculate the value of current in the 4 5 2 resistor and indicate its direction Also calculate the potential difference across each cell E 4V 0 50 4 50 www E 1 00 302 mis 6 0

same 5 The ratio of lengths of two wires made up of material is 2 3 and the ratio of areas of cross section 3 2 The ratio of their resistances is 1 9 4 2 4 9 3 1 3 4 3 1

When a battery sends current through a resistance R for time t the heat produced in the resistor is Q When the same battery sends current through another resistance R for time t the heat produced in R is again C Determine the internal resistance of the battery

the principle of working of a potentiometer ii In the following potentiometer circuit AB is a uniform wire of length 1 m and resistance 10 22 Calculate the potential gradient along the wire and balance length AO 1 A 1 292 www www 12V 1 5 V 15 92 www O G B

Ans 1 13 A resistance wire connected in the left gap of metre bridge balances a 102 resistance in the righ gap at a point which divides the bridge wire in the ratio 3 2 If the length of the resistance wire 1 5 m then the length of 12 of the resistance wi is 1 1 5 x 10 2 m 3 1 0 x 10 m Ans 3 2 1 0 x 10 m 4 1 5 x 10 m

An electrical circuit is given in the figure Power developed in the 1 ohm resistance will be maximum if value of Xis 20 V 100 40 10 Zero www 492 Tyno Text X 492 www Add your responses www 10 Q2 A 19 Asked by 2214907 aesl id Standard XII Stream NEET Aug 2 2021 at 10 34 AM B

Ten cell each of emf E and same internal resistance r are connected in series If due to oversight one cell is connected wrongly then the equivalent e m f of the combination is 12 E 10 E 8 E

5 Five equal resistances each of value R ar connected in a form shown alongside Th equivalent resistance of the network A R R B www D R R R C 1 Between the points B and D is R R 2 Between the points B and D is 2 3 Between the points A and C is 2R R 1 Retween the points A and Cis

Using Kirchhoff s rules determine the value of unknown resistance R in the circuit so that no current flows through 402 resistance Also find the potential difference between A and D 192 www A 192 www TO 9 V E www B 492 6 V 3 V C

A potentiometer consists of a wire of length 8 m and resistance 20 Q It is connected to a cell of e m f 4 V Th potential difference per unit length of the wire will be O 4 V m O 1 V m O 0 5 V m O 5 V m

1 PHYSICS The color code of a resistance is given below Yellow Violet Brown Gold The values of resistance and tolerance respectively are 1 470 2 5 3 47 kn 10 Ans 1 2 470 kn 5 4 4 7 km 5

A wire of resistance 10 2 is bent to form a circle F and Q are points on the circumference of the circle dividing it into a quadrant and are connected to a Battery of 3 V and internal resistance 102 as showr in the figure The currents in the two parts of the circle are 1 2 3 4 6 5 3 V 192 23 A and 26 4 25 15 A and A 26 A and 3 A and 25 18 23 A 12 25 A 9 A 25 P Q

Assertion A In a meter bridge experiment null point for an unknown resistance is measured Now the unknown resistance is put inside an enclosure maintained at a higher temperature The null point can be obtained at the same point as before by decreasing the value of the standard resistance in the other gap Reason R Resistance of a metal increases with decrease in temperature

Three resistance P Q Reach of 3 Q and an unknown resistance S form the four arms of a wheatstone bridge circuit When a resistance of 6 Q is connected in parallel to S the bridge get balanced What is value of S 60 O 40 3Q 90

0 A cell of unknown emfe and internal resistance r two unknown resistances R and R R R and a perfect ammeter are given The current in the circuit is measured in five different situations a Without any external resistance in the circuit b With resistance R only c With resistance R only d With both R and R used in series combination e With both R and R2 used in parallel combination The current obtained in the five cases are 0 42 A 0 6 A 1 05 A 1 4 A and 4 2 A but not necessarily in that order Identify the currents in the five cases listed above and calculate r R and R

uestion No 02 alculate the power dissipated by the 5 volt zener diode for the following values of motor current assume the battery voltage remains constant at olts 3M For motor current 50mA For motor current 140mA 12 volts 50 2 Zener diode

Calculate the power dissipated by the 5 volt zener diode for the following values of motor current assume the battery voltage remains constant at wolts 3M a For motor current 50mA For motor current 140mA 12 volts 50 2 Zener diode

The drift velocity of free electron in a conductor is vo when the current i is following in it If both radius and current are halved the drift velocity will be Vo 2 4V0

potential inside is onstant The charges Q Q Q Q are placed at the vertices of a square of side a n clockwise order The potential at the centre of the square is a Zero b Kq a 2 c Kq a2 d Ko 2a

A Wheatstone bridge has arms of resistances 10 20 30 and 40 A galvanometer of resistance 502 is connected to the junctions of 102 and 40 coils and 20 and 30 coils A 2 V accumulator of negligible resistance is connected to the other two junctions Calculate a the current through the galvanometer and b the resistance between two points where th accumulator is connected Irl

Two circular rings of identical radii and esistance 36 2 are placed as shown in he figure Conducting joints are made t points A and B and a cell of emf 20 V is connected between these two points What is the power in W delivered by the cell C and C are the centres of the two rings C A

If an ideal voltmeter V connected across 4 2 in the circuit shown below shows null deflection then 2Q 4Q 15 V ww R value of R is 192 value of R is 202 Current through 5 V battery will be 0 Current through 15 V battery will be 0 5 V

Two cells of emf E and are joined in series and the balancing length of potentiometer wire 550 cm If the terminal of is reversed the balance length obtained is 150 cm Given E E the ratio will be E E 3 2 c

A The e m f of the driver cell in the potentiometer experiment should be greater than the e m f of the cell to be determined Reason R The fall of potential across the potentiometer wire should not be less than e m f of the cell to be determined 1 Point Both A and R are true and R is the correct explanation of A Both A and R are true but R is NOT the correct explanation of A A is true but R is false A is false and R is also false

When two identical batteries of internal resistance 12 each are connected in series across a resistor R the rate of heat produced in R is J When the same batteries are connected in parallel across R the rate is J2 If J 2 25 J then the value of R in 2 is

1 Point Omotion of conduction electrons due to random collisions OOO motion of conduction electrons due to electric field E repulsion to the conduction electrons due to inner electrons of ions collision of conduction electrons with each other

Question A steady current flows in a metallic conductor of non uniform cross section The quantity quantities constant along the length of the conductor is are L 1 Point current electric field and drift speed drift speed only current and drift speed current only

A galvanometer having a coil resistance 100 2 gives a full scale deflection when a current of 1 mA is passed through it What is the value of the resistance which can convert this galvanometer into a voltmeter giving full scale deflection for a potential difference of 10 V 1 9 9 k 3 7 9 k 2 8 9 k 4 10 km2

27 The arrangement here shows a metallic sphere of radius r carrying charge Q The switch S is initially open The switch is closed at t 0 Charge on the sphere is halved at time t equal to 1 Rr In 4 TEO 2 Rr In 16 TEO 3 Rr In 2 TEO 4 TC Dr Q XX X X X S www R

a Derive an expression for the resistivity of a material in terms of relaxation time number density and mass and charge of charge carriers in it Explain using this relation why the resistivity of the metal increases and that of a semiconductor decreases with rise in temperature b Draw a Graph showing variation of resistivity with temperature for nichrome Which property of nichrome is used to make standard resistance coils

a Are the paths of electrons straight lines between successive collisions with positive ions of the metal in the i absence of electric field ii presence of electric field b Establish a relation between drift velocity Va of an electron in a conductor of cross section A carrying current i and concentration n of free electrons per unit volume of the conductor Hence obtain the relation between current density and drift velocity

A long straight wire carrying current of 25 A rests on a table as shown in figure Another wire PQ of length 1 m mass 2 5 g carries the same current but in the opposite direction The wire PQ is free to slide up and down To what height will PQ rise P h

a State Kirchhoff s laws used in electrical networks b In the electric network shown in the figure use Kirchhoff s rules to calculate the power consumed by the resistance R 4 9 B A E H I I 12 H 12 E 12 V N R 4Q E2 6 V r 20 www C D F

b 4 V 422 www www 292 1 f 692 www 5 V 322 ww 392 13 d 7 V A two ring circuit is given below a Kirchhoff s loop and intersection for both ring Calculate the currents 11 12 and 13 by applying th rules b the potential difference between points a an Calculate Va Vd

Amount of heat generated in the resistance R due to flow of charge q when current in the resistance linearly decreases down to zero in time interval from t 0 to t to q R to 2q R 3 to

Four cells of identical emf and internal resistance are connected in series to a variable resistor The following graph shows the variation of terminal voltage of the combination with current output V in volt 5 6 4 2 2 8 1 4 0 5 1 0 1 5 2 0 in amp a What is emf of each cell b Calculate internal resistance of each cell c For what current from the cells does maximum power dissipation

A closed circuit consists of a source of constant emf of 10 V connected to a resistor of resistance 10 0 and inductor of inductance O 1 H At time t O the inductance was abruptly decreased to 0 01 H Find the current in the circuit at t 0 immediately after change in A

The current through the 5 Q resistance in the network as shown in figure is L 00 5 3 A 40 20 V 2 10 V 1 292 wwww 1 122 www R 59 www

Carbon silicon and germanium have four valence electrons each At room temperature which one of the following statements is most appropriate 1 The number of free conduction electrons is negligibly small in all the three 2 The number of free electrons for conduction is significant in all the three 3 The number of free electrons for conduction is significant only in Si and Ge but small in C 4 The number of free electrons for conduction is significant in C but small in Si and Ge

43 Sixteen resistances each of 5 2 are connected as shown in the figure wwwww www wwww wwww A www wwww www www www 24 V b wwww If a battery of 24 V is connected across the network then current in branch marked ab is 96 48 a c 5 A d 13 A

A 5 wire potentiometer with each wire of 1 m is connected to a storage cell of emf 2 V and resistance 1 2 A primary cell is balanced against middle of the second last wire What resistance will be required in series with the storage cell to push the null point to the centre of the last wire The wire has 3 2 resistance per metre

26 Two bulbs X and Y having same voltage rating and of power 40 watt and 60 watt respectively are connected in series across a potential difference of 300 volt then 1 X will glow brighter than Y 2 Resistance of Y is greater than X 3 Heat produced in Y will be greater than X 4 Voltage drop is same across X and Y

Inside solid conductor electrons m randomly and keep colliding with fixed i If there N electrons and the velocity of the it clea i 1 2 3 N at a given time is v then 1 N v 0 3 2N v 0 2 V V 0 4 None of these

In a circuit shown in figure the heat produced in 5 Q resistor due to current flowing in it is 20 J The heat produced in 6 resistor is 12 J 6 J 20 J 692 www wwwww 592 492 www

The ammeter A reads 4 A and the voltmeter V reads 40 V The value of resistance R is Assuming finite value of resistance of ammeter and voltmeter A Exactly 10 ohm Less than 10 ohm More than 10 ohm www R Information insufficient V

In the network shown below potential difference across PC is 20 22 wwww 5 V 8 V 4 V 10 V HI P 40 Q www wwwww 40 Q

The efficiency of Carnot engine is 50 and temperature of sink is 500 K If temperature of source is kept constant and its efficiency raised to 60 then the required temperature of sink will be A 100 K 2002 C 400 K B 600 K D 500 K

INTEGER ANSWER TYPE A conducting medium is in the form of a quarter of an annulus of radii a and b a with uniform thickness h as shown in figure The conductivity of the material of the medium is uniform The resistance of the specimen between the pair of opposite faces in the direction is X In bla Then Xis Toh 50 TOP 10