Current Electricity Questions and Answers

A set of n identical resistors each of resistance RN when connected in series have an effective resistance X and when the resistors are connected in parallel their effective resistance is Y Find the relation between R X and Y

The internal resistances of two cells shown are 0 1 2 and 0 3 22 If R 0 2 2 the potential difference across the A 2 V 0 192 HH A 0 2 S ww 2 V 0 3 Q fr B cell B will be zero and A will be less than 2 V cell A will be zero and B will be greater than 2 V B C cells A and B will be 2 V D cell A will he Y and will b

When a resistance of 100 2 is connected in series with a galvanometer of resistance R then its range is V To double its range a resistance of 1000 is connected in series Find the value of R a 700 S c 900 S 7 Two cells with b 800 S d 100 S

Eels are able to generate current with biological cells called electroplaques The electroplaques in an eel are arranged in 100 rows each row stretching horizontally along the body of the fish containing 5000 electroplaques The arrangement is suggestively shown below Each electroplaques has an emf of 0 15 V and internal resistance of 0 252 0 15 V Fwwwwwwwww 0 250 Fwwwwwwwww 5000 electroplaques per row a 1 5 A c 15 A Fwwwwwwwww 50002 The water surrounding the eel completes a circuit between the head and its tail If the water surrounding it has a resistance of 5002 the current an eel can produce in water is about 100 rows b 3 0 A d 30 A

An electric network is is constructed with 12 and 2 2 resistors as shown The current through the 2 2 resistor nearest to the battery is A 1 5 A I I I B 2 0 A C 3 0 A D 4 0 A 6 V 19 wwww ods I wwww 222 branada R 2Q

The potentiometer wire of length 100cm has a resistance of 102 It is connected in series with a resistance of 52 and an accumulaot or emf 3V having negligible resistance A source 1 2V is balanced against a length L of the potentionmeter wire find the value of L A 502 www L H 1 2V K B

Find the effective value or rms value of an alternating current that changes according to the law All quantities are in S I unit and symbols have their usual meaning T I 10 when 0 t T 8 I 0 when 8 5 t T 9 I 10 when t T I 0 when T t T I 10 when T t T 2 8 8 8 T 2

is 8 4V when the current is 8A the A 12 4 V battery whose internal resistance is 0 05 2 is charged by an ideal external 14 2 V source of emf Find The thermal power loss The rate at which electrical energy is being converted to chemical energy in the battery a b ambinod to give an equivalent resistance R

Q7 II A bird stands on a dc electric transmission line carrying 3100 A Fig 25 34 The line has 2 5 X 105 resistance per meter and the bird s feet are 4 0 cm apart What is the potential differ ence between the bird s feet FIGURE 25 34 Problem 8

View In English A potential difference V is applied to a copper wire of diameter d and length L There will be no effect on the electron drift speed of doubling which of the parameter 1 2 3 4 Voltage Longth Diameter None

5 In the given figure find the total resistance between the points A and B 60 2 A www 60 2 200 V B wwww 60 12 wwwwwwwwwww 30 2 www 30 2 300 www ww 40 2 40 2 www 26 5 2 15 02 www 892 www 12 02 www 15 2 www 7 15 02 10 2 16 22 24 22 www 15 6 2

In a series LCR circuit the frequencies f and f2 at which the 1 current falls to of the current amplitude at resonance 2 are separated by frequency interval A B C R L 2 VLC VLC Correct Answer

4 With a cell of emf 1 5 V the balance point is obtained at a distance of 60 cm from one end of a potentiometer wire Calculate the potential difference between the two ends of the wire if its total length is 100 cm

Given that the current through 1202 resistance in the network shown is zero Then SRA 3 4 A The value of E is 42V C The resistance r is 302 402 www 292 12 www 60 www www 302 202 ww 12 R 30 www 30 www www 342 120 In 1802 202 ww ww 401 THE B The value of E is 36V D The resistance r is 202

Use of eddy currents is favoured in the following except Induction furnace Speedometer Electromagnetic damping Electric generator

Q No 03 a You are given length of heating wire made of nickel chromium iron Alloy called Nichrome It has a resistance of 722 Under what circumstances the wire will dissipate more power a It is to be connected across a 120 V line b The wire is cut in half pieces and two halves are connected in parallel across the line

The circuit shown has 5 resistors of equal resistance R Calculate equivalent resistance across points A and B A B Fun

R 1 2 k R3 3 3 k 15V E E 5V VR R 2 2kQ

2 point A metre bridge is balanced with a 20 S2 resistance in the left gap and a 302 resistance in the right gap If 20 resistance is now shunted with another 20 resistance find the shift in the null point O 25 cm to the right O 25 cm to the left O 15 cm to the left O 15 cm to the right

Five equal resistances each of resistance R are connected a shown in figure A battery of Vvoltage is connected between points A and B The current flowing in AFCEB section will be C D R 3V R 2V R R B R E

3 3 A 25MVA 11kV generator has a X 0 2 pu Its negative and zero sequence reactances are 0 3pu and 0 1 pu respectively The neutral of the generator is solidly grounded Determine the sub transient current in the generator and the line line voltages for sub transient conditions when a line earth fault occurs at the generator terminals Assume that before the occurrence of the fault the generator is operating at no load at rated voltage Ignore resistances

9 Consider a circuit as shown in figure Then choose CORRECT statement s 20 30 wwww 502 10V 492 69 A If 40 resistance is shorted resistance less wire connected in parallel to it the current through battery will increase B If 40 resistor is shorted the current through 502 resistance will decrease C If instead of 402 502 resistor is shorted current through battery will decrease D If instead of 40 30 resistor is shorted current through battery will decrease

A current I flows through a cylindrical rod of uniform cross section area A and resistivity p The electric flux through the shaded cross section of rod as shown in figure is shaded cross section O2pl T O pl

An inductor of inductance 2 0 mH is connected across a charged capacitor of capacitance 5 F and the resulting L C circuit is set oscillating at its natural frequency Let Q denote the instantaneous charge on the capacitor and i the current in the circuit It is found that the maximum value of Qis 200 C Now answer the following questions based on the information given above When Q 100 C the value of is 10 2p A s value of p is di dt

Potentiometer wire is 10 m long and has a resistance of 2 Q m It is connected in series with the battery of EMF 3 V and resistance of 100 The potential gradient along the wire in V m is O 0 02 O 0 01 O 0 2 O 0 1 2 p

A current of 200 mA flows in a silver wire of radius 0 8 mm Find The drift speed of the electrons The electric field within the wire The free electron density is 5 8 x 1028 m Take p 1 5x10 22 a b

Four resisters P Q R and S having resistance 30 30 40 and 602 respectively arrange to form a Wheatstone s bridge value of resistance with which S must be shunted in order to balance the bridge is O 30 O 120 O 40 16 0 2 poi

If the circuit implemented by you is ON for 15 minutes with following componen connected in parallel What is the total cost of using them at Rs 3 45 per Kwh a 100W resistor b Six 50W series resistor combination c 40W motor

The function of shunt in ammeter is O O O a to increase the resistance of galvanometer b to allow minimum current through the galvanometer c to reduce the resistance of galvanometer O d both b and c 1 point e all a b and c

respectively the specific conductivity varies as o x 0 where x is distance along the axis of cylinder from one end A l VX I If the potential drops along the cylinder is Vo electric filed at each point in the cylinder is E NV x find the value of N

Three 10 resistors are connected from point A to point X from point X to point Y and from point Y to point B A 20 V battery with an internal resistance of 20 02 is connecte negative terminal to A and positive to B A 10 V battery with an internal resistance of 10 C is connected negative terminal to Y and positive to X i Draw the circuit diagram ii Calculate the potential difference between X and Y

4 decreases by 1 103 If a battery of fixed emf e and internal resistance r is connected to a variable external resistance R then the condition for which the power delivered by the battery to the load will be maximum is 1 r R 2 3 r 4R 2 r R R 3 4 r

4 Depends upon the voltage of battery 76 The effective resistance between A and B is R 3 A B R 2 www R www R 2 R R 2 R 3R 4 2R 4 77 Colour code in a resistor is given by bar

3 4 4 2R 7 Colour code in a resistor is given by bands of colours orange yellow brown The value of resistance is 1 34 x 102 10 3 24 x 102 2 10 2 34 10 2 20 4 24 x 104 0 10 83

Aakash Institute 54 Two bulbs A and B are connected in series across a 250V supply Identify the correct statement 220V 100W 110V 60W A B 250V 1 None of the bulb glows 2 Both the bulbs glow with same intensity 3 The potential difference across both the bulbs are equal TAL 1 50 59 The 4x ave be 1 3 60 Thr SOL sam sam 1

The emf of a cell is and its internal resistance is r Its terminals are connected to resistance Reto The potential difference between the terminal is for R 402 and 1 8V for R 90 Then 1 1V r 10 2 2V r 10 3 2V r 20 4 2 5V r 0 50 Telegram heeta 6

4 3 4 58 The n rows each containing m cells in series are joined in parrallel Maximum current is taken from this combination across an external resistance of 352 If the total number of cells used are 24 and internal resistance of each cell is 0 52 then 1 m 8 n 3 3 m 12 n 2 2 m 6 n 4 4 m 2 n 12 3 64 The follo A 2 3 2

A cell emf 3V and internal resistance 0 750 is connected to a nonlinear conductor whose V I g raph is shown in figure obtain graphically the current drawn from the cell and its terminal voltage 6 5 4 3 2 1 0 E 1 1 1 1 1 2 3 V

60 The potential difference between A and B in the following circuit is 40 www 1 1 4 V 3 2 2 V 502 www 402 wwwww A B wwww 40 1 1 2 V 2 0 4 V 4 1 2 V

B A battery of internal resistance 42 is connected to the network of resistances as shown in figure In order that maximum power is delivered to the network the value of R in 2 should be E T4 2 R www R www R www www R www 6R 4R wwww R

intensity 55 A current of 5 A is passing through a metallic wire of cross sectional area 4 10 m If the density of the charge carriers in the wire is 5x1026 m the drift velocity of the electrons is 1 1 16 m s 1 3 m s 64 2 4 1 32 m s 1 128 m s

V 3 tan 4 tan 24 In the circuit shown the value of resistance R if the total voltage is in phase with the total current is nearly 2092 wwww 1 24 S 2 89 3 12 Q R R TC 2 Xc 40 52 HI mooooo X 48 Q 100 2 sinot V 1 100 W 2 120 W 3 115 W 4 110 W 27 A 8 F capacitor is charged to 40 V Battery is then disconnected and inc 80 mH is connected across the capacitor LC oscillations are set up The maximur in the coil will be 1 0 4 A 2 0 6 A 3 0 8 A

it and coefficient of thermal conductivity K and ternating blocks of length respectively as shown in figure The cross sectional coefficient of thermal conductivity of the wall between area of the blocks are the same The equivalent 2017 Gujara left and right is a K K 2 K K 3 Two identical t C sists of K K K K K K b 2K K K K 2 d 3K K K K 11 TH ter flc ma rat a C 12 The of in tem a O c 0 13 Cert first temp a 45 c 42 14 Stear Whe

35 For maximum power developed in the circuit the value of the internal resistance r must be if all the cells are identical each of emf E and the internal resistance r 3 1 5 3 3 r 72 www 192 www R 0 www 3 2 r 22 3 4 r 02 72

194 A battery of internal resistance 4 2 is connected to the network of resistance as shown in the figure 4 a Q 9 E 39 R www S2 R www R www 6R In order to give the maximum power to the network the value of R should be 4R www b d 1618 R C II

3 0 3 4 0 4 24 Four cells each of emf E and internal resistance r are connected in series to form a loop ABCD Find the potential difference across AB 1 2E A www www DT ww T B HE 2 E

Current Electricity 26 In the given circuit shown in figure the potentia difference between battery 2 will be 1 5 5 volt 3 3 volt E 10V E 4V www www r 102 r 192 www R 202 2 8 5 volt 4 3 5 volt

2 10 2 4 2 5 2 of resistance R decreases h shown in the figure then uced in the coil is 3 1x F 4 Ixr 13 A wire has non uniform cross section as shown in figure A steady current flows through it The drift speed of electrons at points P and Q is V and Vo is V Vo OXY O o 1 V Vo 2 W W 2 V Vo A

Aakash Institute ntial 31 3n identical cells each of emf E and internal resistance r are connected in series to form a closed circuit If out of 3n cells n cells are wrongly connected then the terminal voltage across any one cell which is connected wrongly is 1 3 4E 3E 2 2 4 2E 3 3E 4

To make the resistance 4 5 times of a uniform wire a part of its length was uniformly stretched till the fina length of the entire wire becomes double the original length What percentage of the wire was stretched 1 60 5 2 33 3 4 50 3 66 7