Current Electricity Questions and Answers

Jasthan Heat is flowing through a conductor of length I from x 0 to x 1 If its thermal resistance per unit length is uniform which of the following graphs is correct 1 3 E TA K 11 O T

28 The length of potentiometer wire is 1 m and its 28 Ha resistance is 4 22 A current of 5 mA is flowing in it An unknown source of emf is balanced on 40 cm length of this wire The emf of the source is ufarte 1 fa 40 cm 1 5 mV 2 6 mV 3 12 mV 4 8 mV 1 5 m 3 12 r

6 Two bulbs whose resistances are in the ratio 2 3 are connected in series with a steady voltage source The ratio of powers expended in the bulbs will be 1 3 2 3 2 3 2 4 9 4 1 2 26 3 1 at de 1

of the bridge if AC corres ponding to null defle ction of galvanometer is x what would be its value if the radius of the A wire AB is doubled or R Solution For null deflection of galvanometer in a metrebridge experiment R X R 100 x X R RAC R RCB Since R R remains constant x 100 x also R

In a part of a network shown if at an instant current 10 A and it is decreasing at the rate of 5 As then find the value of potential difference V V at that instant in V 4Q 10V 2Q 2 H

Maximum and minimum radii of given cylindrical conductor PQ are r and then current through the battery will be p resistivity 1 E Question Type Single Correct Type 2 Er r pl 1 2 2 Er r

A reactance bridge arrangement replaces the resistor in a Wheatstone bridge with a capacitor or inductor Such a reactance bridge is then excited by an AC voltage Consider the following bridge arrangement Show that the balance equations for this bridge are given by C C R R R R

27 All the diodes are ideal The current flowing in resistor connected between the diodes D anc is 1 1A 2 20 192 D D D 292 www 7 9 D ww 492 192 D4 59 www 10V 30 2 2A 1 Zero

1 In the given circuit the switch is closed at t 0 The ratio of electric current through resistance R at t 0 and at t is 1 32 R R www www R R 2 4 3 4 2 3 www00000 R R

16 To draw maximum current from a combination of cells how should the 2 points cells be grouped O a Series Ob Parallel O c Mixed O d depends upon the relative values of internal external resistance

statement regarding the circuit 202 1 6V 892 4 F 2 F 40 Just after the switch S is closed I1 3A 12 0A and 13 0 Long time after the switch S is closed 11 12 13 0 6A Long time after the switch S is closed 1 0 6A 12 0 and 13 0 Just after the switch S is closed I 3A

A coil of inductance L 27H and R 12 is connected to a source of constant emf E 3V A resistance Ro 22 is connected in parallel with the coil Find the heat generated in the coil after the switch S is disconnected The internal resistance of the source is negligible Express your answer in J L R Ro PARK

Q No 12 An electric bulb is rated 220 V and 100 watt Resistance of bulb when operated on 110 volt will be 1 3 Correct Answer 2 1210 484 02 25 Q2 242 Q

93 A current is flowing through a cylindrical conductor of radius R such that current density at any cross section is given by J J where r is the radial distance from the axis of the cylinder Calculate the total current through the cross section 1 3 J R 2 2 J R 2 J R 3 J NR 4 6

A branch of a circuit is shown in the figure If current is decreasing at the rate of 10 As the potential difference between A and B is AP EAMCET Engg 2016 2A wwww 792 LA IV C 10V 4V momo 9 mH B 5V D 2V B

A galvanometer of coil resistance I 2 is converted into voltmeter by using a resistance of 5 in series and same galvanometer is converted into ammeter by using a shunt of 1 Now ammeter and voltmeter connected in circuit as shown find the reading of voltmeter and ammeter V www 652 www www 1592 152 4 592 30 V A W 1292 Rate this question

12 Ammeter is always used O a in series with the element through which current is to be determined Ob in parallel with the element through which current is to be determined Oc to simulate the element across which voltage is to be determined d to simulate the element through which resistance is to be determined

an applied electric field will polarise the polar dielectric material reason in polar dielectric each molecule has a permanent dipole moment but these ar e randomly oriented in the absence of a nd externally applied electric field assertion if a point charge q is placed in front of an infinite grounded conducting plane s urface the point charge will experience a force reason this force is due to the induced charge on the conducting surface which is at z

A 6 The diagram shows an electric circuit 152 resistor T battery ammeter lamp A 1 g Another 150 resistor is connected in parallel with the 150 resistor that is already in the circuit i What is the combined resistance of the two 15 resistors in parallel 300 150 7 5 or zero ii State what effect if any adding this extra aristor har on the TUINEAL lamp 2

After being closed for a long time the switch 5 in the circuit shown in the figure below is thrown open at t 0 In the circuit 24 0 V R 4 50 kn R 6 90 kn and L 513 mH RB voo a Lb a What is the emf across the inductor immediately after the switch is opened b When does the current in the resistor Re have a magnitude of 1 00 mA

6 The diagram shows an electric circuit 152 resistor battery lamp ammeter d i Name the instrument that would be needed to measure the potential difference p d across the 150 resistor ii Using the correct symbol add this instrument to your circuit diagram in c in a position to measure the p d across the 150 resistor 2

The length area of cross section and density of a metallic wire are respectively 1 m 10 6 m and 5x10 kg m Assuming that each atom contributes one free electron find the drift velocity of electrons if a current of 16 A flows through it Given that the atomic wt of the metal is 60 g mol 1 2 m s 2 0 2 m s 3 2 10 3 m s 4 2 10 2 m s

ER In the figure internal resistance of the cell is negligible If resistance R is decreased A Current through R increases C The voltage drop across R decreases E None of these B Current through R decreases D The power dissipation by R decreases

Ick out the wrong statement In a simple battery circuit the A point of lowest potential is the negative terminal of the battery The resistance of an incandescent B lamp is greatest when the lamp is switched off C D An ordinary 100 W lamp has less resistance than a 60 W lamp At constant voltage the heat development in a uniform wire varies inversely as the length of the wire used

A moving coil galvanometer is converted into an ammeter reading up to 0 03 A by connecting a shunt of resistance r 4 What is the maximum current which can be sent through this galvanometer if no shunt is used Here r resistance of galvanometer 1 0 004 A 2 0 005 A

Consider a simple circuit shown in Fig variable resistance R R can vary from R to infinity ris internal resistance of the battery r R R Potential drop across AB is nearly constant as R is varied b Current through R is nearly a constant as R is varied c Current I depends sensitively on R Give Reais always Shon d I V T R ductors

Charge Q flowing through a resistance R varies with time t as Q at bt Total heat produced in R is fRQ at bt Options a R 6b 1 2 TRR 3 a R 3b a R 2b

The measurement of an unknown resistance R is to be carried out using Wheatstones bridge see Fig 3 25 of NCERT Book Two students perform an experiment in two ways The first students takes R 1022 and R 52 The other student takes R 10000 and R 50022 In the standard arm both take R 50 Both find R R 2 R 1022 within errors R a The errors of measurement of the two students are the same b Errors of measurement do depend on the accuracy with which R and R can be measured c If the student uses large values of R and R the currents through the arms will be feeble This will make determination of null point accurately more difficult d Wheatstone bridge is a very accurate instrument and has no errors of measurement

max Let there be n resistors R R with R max R R and R min R R Show that when they are connected in parallel the resultant resistance R Rin and when they are connected in series the resultant resistance R Rax Interpret the result physically WPAG

The resistance of a wire at room temperature 30 C is found to be 10 2 Now to increases the resistance by 10 the temperature of the wire must be The temperature coefficient of resistance of the material of the wire is 0 002 per C A 36 C B 83 C C 63 C D 33 C

Suppose there is a circuit consisting of only resistances and batteries and we have to double or increase it to n times all voltages and all resistances Show that currents are unaltered Do this for circuit of Example 3 7 in the NCERT Text Book for Class XII

Consider a current carrying wire current I in the shape of a circle Note that as the current progresses along the wire the direction of j current density changes in an exact manner while the current I remain unaffected The agent that is essentially responsible for is a source of emf b electric field produced by charges accumulated on the surface of wire c the charges just behind a given segment of wire which push them just the right way by repulsion d the charges ahead

The potential difference in open circuit for a cell is 2 2 V When a 42 resistor is connected between its two electrodes the potential difference becomes 2 V The internal resistance of the cell will be A 102 B 0 22 C 2 502 040

A cell has terminal voltage 2V in open circuit and internal resistance of the given cell is 202 If 4A of current is flowing between points P and Q in the circuit and then the potential difference between P and Q is 21 202 P A 4A C 22V B 24V 30V wwww Q 402

N emf varies directly with the internal resistance as per the equation Ex 3 51 are connected as shown in the figure Assume that the length of the wire that is used to connect the circuit is 15 m long Then the value of current I in the circuit is 1 2 A r 1 15 4 A 35 A 3 13 14 15 16 5 6

In copper each copper atom releases one electron If a current of 1 1 A is flowing in the copper wire of uniform cross sectional area of diameter 1 mm then drift velocity of electrons will approximately be Density of copper Atomic weight of copper 63 A 10 3 mm s B 0 1 mm s C 0 2 mm s 9 10 kg m D 0 2 cm s

1cmx100cm If specific resistance of its material is 3 10 7 m then the resistance between the opposite rectangular faces is A 3 x 10702 3 10 C 3 x 10 52 B 3

An energy source will supply a constant current into the load if its internal resistance is A equal to the resistance of the load B C D very large as compared to the load resistance zero non zero but less than the resistance of the load

When a copper voltmeter is connected with a battery of e m f 12 volt 2 gm of copper is deposited in 30 minutes If the same voltmeter is connected across a 6 V battery then the mass of the copper deposited in 45 minutes would be A 1 gm B 1 5 gm c 2 gm

Two batteries with e m f 12 V and 13 V are connected in parallel across a load resistor of 102 The internal resistances of the two batteries are and 12 respectively The voltage across the 22 load lies between A 11 7 V and 11 8 V B C D 11 6 V and 11 7 V 11 5 V and 11 6 V 11 4 V and 11 5 V

32 For a cell the graph between the potential difference V across the terminals of the cell and the current I drawn from the cell is shown in the figure The emf and the internal resistance of the cell are a 2 V 0 522 V volt 2 0 1 5 1 0 0 5 0 1 2 3 5 ampere 4 b 2 V 0 4 2 d 2 V 0 4 0 th networ

E internal resistance r 0 5 a storage A dc source OT battery of emf E 90 V and an external resistance R are connected as shown in figure For what value of R no current will pass through the battery E E 4 1 A B C E R r 0 5 5 5 Q 3 5 Q 4 5 Q

Sir in this I have used formula of power v2 R but answer is according to the formula of power i2 R Please correct me sir where I am wrong why I cannot use formula but I have mentioned Two bulbs whose resistances are in the ratio 2 3 are connected in series with a steady voltage source The ratio of powers expended in the bulbs will be 3 2 4 9 2 3

n identical cells are joined in series with its two cells A and B in the loop with reversed polarities EMF of each shell is E and internal resistance r Potential difference across cell A or B is here n 4 A B C D 2E 2E 1 1 4E n 2E 1 2

vii In silicon p n junction diode the width of depletion region ranges from a 0 5 mm to 1 nm c 50 pm to 100 m vili Water rises in anille b 0 5 m tolum d 50 nm to 100 nm

Two batteries one of the emf 3V resistance 1 ohm and the other of emf 15 V internal resistance 2 ohm are connected in series with a resistance R as shown If the potential difference between a and b is zero the resistance of R in ohm is a 3V 192 A 5 B 7 15V 202 wir

The diagram below shows a circuit used in an experiment to determine the emf and internal resistance of the cell C A graph was plotted of the potential difference V between the terminals of the cell against the current I which was varied by adjusting the rheostat The graph is shown on the right x and y are the intercepts of the graph with the axes as shown What is the internal resistance of the cell mo E V V I A

A 6 0 volt battery is connected to two light bulbs as shown in figure Light bulb 1 has resistance 3 ohm while light bulb 2 has resistance 6 ohm Battery has negligible internal resistance Which bulb will glow brighter A Bulb 1 Bulb 2 311111 6 0 V Bulb 1 will glow more first and then its brightness will become less than bulb 2

Infinite number of internal resistance E 9657 2 2 n n connected in series in same manner across an E r E n n E r 39 3 n nr external resistance of n 1 through the external resistor is n are Current flowing

Answer given is 2 15 A capacitor of capacitance C is initially charged to a potential difference of V Now it is connected to a battery of 2V with opposite polarity The heat developed is 1 2 2 CV 2 CV 3 CV 92 JUI Hius