Question

I need all difficult class 10 ICSE physics numericals

Answer 1

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Numerical Questions for electricity 
a) Concepts questions
b) Calculation problems
c) Multiple choice questions
d) Long answer questions
e) Fill in the blank's
 1)  A wire of length 3 m and area of cross-section 1.7X10-6 m2 has a resistance 3X10-2ohm.
a) What is the formula for resistivity of the wire and what is the unit of it
b) Calculate the resistivity of the wire
Ans)
a) Resistivity of the wire is given by

ρ=R

A

L


And It unit is Ohm-m
b) In this case
L=3 m
A=1.7X10-6 m2
R=3X10-2 ohm
So
ρ=1.7X10-8 Ohm-m
2) The table given below shows the resistivity of three Material X, Y and Z?

Samples

X

Y

Z

Resistivity

3 X10-9

11.1 X10-6

18X10-17

a) Arrange the samples in increasing order of conductivity
b) Which of these is best conductor?
c) Which are these is best insulator?
Ans)
a) Conductivity is inversely proportional to resistivity
So
Y< X< Z
b) Z is the best conductor as it has least resistivity
c) Y is the best insulator as it has highest resistivity
3)  There are m resistor each of resistance R. First they all are connected in series and equivalent resistance is X. Now they are connected in parallel and equivalent resistance is Y.  What is the ratio of X and Y?
Ans)
Series combination
X=R+R+R+…….= mR
Parallel combination

1

Y

=

1

R

+

1

R

+

1

R

+...=

m

R


Or  Y=R/m
So X : Y=m2 : 1

4) We have  four resistors A ,B ,C and D of resistance  4ohm,8ohm ,12 ohm and 24 ohm respectively?

1

Lowest resistance which can be obtained by combining these four resistors

2

highest resistance which can be obtained by combining these four resistors

Ans)
Lowest resistance is obtained in parallel combination

1

R

=

1

4

+

1

8

+

1

12

+

1

24


Or R=2Ω
Highest resistance is obtained in series combination

R=4+8+12+24=48Ω


5)  Three resistors  5Ω, 10Ω and 30Ω are connected in parallel with the battery of Voltage  6V?

S.no

Questions

1

The value of current across each resistor

2

The value of Potential difference across each resistor

3

Total current in the circuit

4

Effective resistance of the circuit

Ans)
Potential difference remains same across parallel combination
So current in each resistor is calculated as
I1=V/R1=6/5=1.2 A
I2=V/R2=6/10=.6 A
I3=V/R3=6/30=.2 A
Total current in the circuit
I=I1+I2+I3=1.2+.6+.2=2 A
Effective resistance

1

R

=

1

5

+

1

10

+

1

30


R= 3Ω




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