cbse class 10 physics science electricity current ammeter voltmeter

1. Electricity
Class – 10
Aditya Mishra
Email: adityakumar2009@gmail.com
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2. Ammeter :
• An instrument used to measure the amount of electric current
flowing through an electric circuit is called ammeter.
• Always connected in series
Symbol :
AMMETER
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3. AMMETER
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4. VOLTMETER
Voltmeter :
• An instrument used to measure the potential difference
between any two point in an electric circuit is called voltmeter
• Always connected in parallel
Symbol :
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5. VOLTMETER
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6. RESISTANCE IN SERIES
R1 R2 R3
• Current through (I) the resistances is same
• Potential difference (V) across each resistor is different
I I
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7. 1 2 3
Total potential difference:
V = V + V + V
V = I R
1 1
V = I R
2 2
V = I R
3 3
V = I R
1 2 3
I R = I R + I R + I R
 
1 2 3
I R = I R + R + R
 
1 2 3
R = R + R + R
eq 1 2 3
R = R + R + R
------- (1)
------- (2)
------- (3)
------- (4)
------- (5)
Substituting equation 2,3,4 and 5 in equation 1
------- (6)
RESISTANCE IN SERIES
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8. eq
R = R + R + R
eq
R = 3R
eq
R = R + R + R + .......
eq
R = n R
---------------- (7)
---------------- (8)
• Equivalent resistance for three resistances each having a value of
R in series combination :
• Equivalent resistance for ‘n’ resistances each having a value of
R in series combination :
RESISTANCE IN SERIES
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9. Q.1 Three resistances each of 3 ohms are connected in series.
Find the equivalent resistances for the combination ?
R = 3 Ω
n = 3 
eq
R = ?
Given :
To Find :
Solution :
For series combination
eq
R = n R
eq
R 3 3
 
R = 9 
Ans :
Problems
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10. Q.1 A 100 resistances when arranged in series combination the
equivalent resistance of the combination is 5000 ohms. What is
the resistance of each resistor ?
n = 100
eq
R = 5000 
R = ?
Given :
To Find :
Solution :
For series combination
eq
R = n R
eq
R
R =
n
5000
R =
100

R = 50 
Problems
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