Q 1 :

A wire of resistance R and length L is cut into 5 equal parts. If these parts are joined parallely, then resultant resistance will be                       [2024]

 

  • 1/25 R

     

  • 1/5 R

     

  • 25 R

     

  • 5 R

     

(1)       

            Resistance of each part = R5

            Total resistance = 15×R5=R25

 



Q 2 :

In the given figure R1=10Ω,R2=8Ω,R3=4Ω and R4=8Ω. Battery is ideal with emf 12 V. Equivalent resistance of the circuit and current supplied by battery are respectively           [2024]

  • 10.5Ω and 1.14A

     

  • 12Ω and 1A

     

  • 10.5Ω and 1A

     

  • 12Ω and 11.4A

     

(2)

Here R2,R3,R4 are in parallel,

1R234=1R2+1R3+1R4R234

R234 is in series with R1, so

Equivalent resistant, Req=R234+R1=2+10=12Ω

The current supplied by the battery, i=1212=1A



Q 3 :

The equivalent resistance between A and B is:             [2024]

  • 18Ω

     

  • 25Ω

     

  • 27Ω

     

  • 19Ω

     

(4)

Req=5Ω+6Ω+8Ω=19Ω

 



Q 4 :

The effective resistance between A and B, if resistance of each resistor is R, will be               [2024]

  • 23R

     

  • 8R3

     

  • 5R3

     

  • 4R3

     

(2)

From symmetry we can remove two middle resistances. New circuit is

 



Q 5 :

Twelve wires each having resistance 2Ω are joined to form a cube. A battery of 6V emf is joined across points a and c. The voltage difference between e and f is ____ V.   [2024]



(1)

 Req=R×3RR+3R=34RReq=34×2=32Ω

 Current through battery =6×23=4A

The current through a-h,iah=48×2=1A

  V across e-f=iah2×R=12×2=1V



Q 6 :

A wire of resistance 20 Ω is divided into 10 equal parts, resulting pairs. A combination of two parts are connected in parallel and so on. Now resulting pairs of parallel combination are connected in series. The equivalent resistance of final combination is ____ Ω.             [2024]



(5)

Resistance of each part R=2010=2Ω

2 parts are connected in parallel R'=22=1Ω

Now, there will be 5 parts, each of resistance 1Ω, they are connected in series.

Req=5R'Req=5Ω



Q 7 :

Equivalent resistance of the following network is _______ Ω.                [2024]



(1)

Req=3×13=1Ω



Q 8 :

Find the equivalent resistance between two ends of the following circuit.          [2025]

  • r

     

  • r6

     

  • r9

     

  • r3

     

(3)

 1Req=1r3+1r3+1r3

Or Req=r9



Q 9 :

A wire of resistance R is bent into an equilateral triangle and an identical wire is bent into a square. The ratio of resistance between the two end points of an edge of the triangle to that of the square is          [2025]

  • 9/8

     

  • 8/9

     

  • 27/32

     

  • 32/27

     

(4)

For the wire bent into an equilateral triangle, each side has a resistance R3

Req=(2R3)(R3)2R3+R3=2R9=R1   (lets say)

.For the wire bent into a square, each side has a resistance R4

.Req=(3R4)(R4)3R4+R4=3R16=R3   (lets say)

 R1R3=2R93R16=3227



Q 10 :

A wire of length 25 m and cross-sectional area 5 mm2 having resistivity of 2×106Ωm is bent into a complete circle. The resistance between diametrically opposite points will be         [2025]

  • 12.5 Ω

     

  • 50 Ω

     

  • 100 Ω

     

  • 25 Ω

     

(none)

Let R be total resistance across ends of wire, then

R=ρLA=2×106×255×106=10Ω

Req=R4=104=2.5Ω



Q 11 :

From the combination of resistors with resistance values R1=R2=R3=5Ω and R4=10Ω, which of the following combination is the best circuit to get an equivalent resistance of 6Ω?          [2025]

 

  •  

  •  

  •  

  •  

(1)

1Req=110+115=3+230=16  Req=6Ω



Q 12 :

A wire of resistance R is bent into a triangular pyramid as shown in figure with each segment having same length. The resistance between points A and B is R/n. The value of n is:          [2025]

  • 16

     

  • 14

     

  • 10

     

  • 12

     

(4)

As, r=R6

(As balanced wheat stone bridge is formed)

Now, Equivalent resistance between A and B can be written as

Clearly, R1=r6

So, RAB=R12R12R1

 1RAB=1R1+12R1+12R1=42R1=2R1

 RAB=R12=r12



Q 13 :

A wire of resistance 9Ω is bent to form an equilateral triangle. Then the equivalent resistance across any two vertices will be ____ ohm.          [2025]



(2)

9Ω is the resistance of whole wire

  Resistance of each wire = 3Ω

  Equivalent resistance = 2Ω

 



Q 14 :

As shown in the figure, a network of resistors is connected to a battery of 24 V with an internal resistance of 3Ω. The currents through the resistors R4 and R5 are I4 and I5 respectively. The values of I4 and I5 are                      [2023]

  • I4=85A and I5=25A

     

  • I4=65A and I5=245A

     

  • I4=25A and I5=85A

     

  • I4=245A and I5=65A

     

(3)

Equivalent resistance of circuit

Req=3+1+2+4+2=12 Ω

Current through battery i=2412=2 A

I4=R5R4+R5×2=520+5×2=25 A

I5=2-25=85 A



Q 15 :

The equivalent resistance between A and B is                      [2023]

  • 23Ω

     

  • 12Ω

     

  • 32Ω

     

  • 13Ω

     

(1)

1Req=12+112+14+16+12

           =6+1+3+2+612=1812=32

  Req=23Ω



Q 16 :

The equivalent resistance between A and B of the network shown in the figure:                     [2023]

  • 112R3

     

  • 14R

     

  • 21R

     

  • 83R

     

(4)

Wheatstone bridge is in balanced condition.

1Req=14R+18RReq=8R3



Q 17 :

Equivalent resistance between the adjacent corners of a regular n-sided polygon of uniform wire of resistance R would be             [2023]

  • (n-1)Rn2

     

  • (n-1)R(2n-1)

     

  • n2R(n-1)

     

  • (n-1)Rn

     

(1)

Suppose resistance of each arm is r, then r=Rn

Req(AB)=R1R2R1+R2

=r(n-1)rr+(n-1)r=r(n-1)rnr=n-1nr=(n-1)Rn2



Q 18 :

The equivalent resistance between A and B as shown in the figure is                    [2023]

  • 5 kΩ

     

  • 20 kΩ

     

  • 10 kΩ

     

  • 30 kΩ

     

(1)

All resistors are in parallel.

So, 1Req=110+120+120

         Req=5 kΩ



Q 19 :

The equivalent resistance of the circuit shown below between points a and b is                 [2023]

  • 24Ω

     

  • 3.2Ω

     

  • 20Ω

     

  • 16Ω

     

(2)

The circuit can be reduced to

  Req=16×416+4=165Ω=3.2Ω



Q 20 :

Given below are two statements:                                       [2023]

Statement I: The equivalent resistance of resistors in a series combination is smaller than the least resistance used in the combination.

Statement II: The resistivity of the material is independent of temperature.

In the light of the above statements, choose the correct answer from the options given below:

  • Statement I is false but Statement II is true

     

  • Both Statement I and Statement II are false

     

  • Statement I is true but Statement II is false

     

  • Both Statement I and Statement II are true

     

(2)

Req=R1+R2+R3  St-1 False

Resistivity depends on temperature.  St-2 False



Q 21 :

In the given circuit, the current (I) through the battery will be             [2023]

  • 1.5 A

     

  • 1 A

     

  • 2.5 A

     

  • 2 A

     

(1)

In the circuit D1 and D3 are forward biased and D2 is reverse biased.

  I=1020/3=10×320=32 A=1.5 A



Q 22 :

In the given circuit, the equivalent resistance between the terminal A and B is ________ Ω.           [2023]



(10)

RAB=3+1+6=10Ω



Q 23 :

If the potential difference between B and D is zero, the value of x is 1nΩ. The value of n is ______.         [2023]



(2)

23=xx+1x

23=1x+1

x=0.5=12

n=2



Q 24 :

10 resistors each of resistance 10Ω can be connected in such a way as to get maximum and minimum equivalent resistance. The ratio of maximum and minimum equivalent resistance will be ________.         [2023]



(100)

Maximum resistance occurs

When all the resistors are connected in series combination

 Rmax=10R

Here R=10Ω

Minimum resistance occurs

When all the resistances are connected in parallel combination

Rmin=R10

 RmaxRmin=100



Q 25 :

A wire of uniform resistance λ Ω/m is bent into a circle of radius r and another piece of wire with length 2r is connected between points A and B (AOB) as shown in the figure. The equivalent resistance between points A and B is _______ Ω.               [2026]

  • 2πλr

     

  • 3πλr8

     

  • 6πλr3π+16

     

  • (π+1)2rλ

     

(3)

1RAB=2λπr+1λ·2r+2λ·3πr

=1λr[2π+12+23π]

=1λr(12+3π+46π)=1λr(16+3π6π)

RAB=λr(6π16+3π)



Q 26 :

A regular hexagon is formed by six wires each of resistance rΩ and the corners are joined to the centre by wires of same resistance. If the current enters at one corner and leaves at the opposite corner, the equivalent resistance of the hexagon between the two opposite corners will be              [2026]

  • 34r

     

  • 45r

     

  • 58r

     

  • 35r

     

(2)

Req=2R×4R32R+4R3=8R210R=45R



Q 27 :

Two known resistances of RΩ and 2RΩ and one unknown resistance XΩ are connected in a circuit as shown in the figure. If the equivalent resistance between points A and B in the circuit is XΩ then the value of X is ______Ω.     [2026]

  • (3-1)R

     

  • 2(3-1)R

     

  • R

     

  • (3+1)R

     

(1)

(2R+x)(R)3R+x=x

x2+2Rx-2R2=0

x=(3-1)R



Q 28 :

The equivalent resistance between the points A and B in the following circuit is x5Ω. The value of x is __________.    [2026]



(21)

6i1+3(2i1-i)=3(i-i1)

15i1=6ii1=25i  ...(1)

3(i-i1)+6i1=1

3i+3i1=1

(3+65)i=1

i=521 A=1VReqReq=215 Ω