Use the data in the table to answer the following – Table shows electrical resistivity of some substances at 20 ° C . Substances Material Resistivity (Ω m) Conductors Silver 1 . 60 × 10 – 8 Copper 1 . 62 × 10 – 8 Aluminium 2 . 63 × 10 – 8 Tungsten 5 . 20 × 10 – 8 Nickel 6 . 84 × 10 – 8 Iron 10 . 0 × 10 – 8 Chromium 12 . 9 × 10 – 8 Mercury 94 . 0 × 10 – 8 Manganese 1 . 84 × 10 – 6 Alloys Constantan (alloy of Cu and Ni ) 49 × 10 – 6 Manganin(alloy of Cu , Mn and Ni ) 44 × 10 – 6 Nichrome (alloy of Ni , Cr , Mn and Fe ) 100 × 10 – 6 Insulators Glass 10 10 – 10 14 Hard rubber 10 13 – 10 16 Ebonite 10 15 – 10 17 Diamond 10 12 – 10 13 Paper (dry) 10 12 Which among iron and mercury is a better conductor?

The resistivity of iron is 10 . 0 × 10 - 8 Ω m whereas resistivity of mercury is 94 . 0 × 10 - 8 Ω m . Therefore, iron is good conductor compared to mercury as resistivity is low for iron. Note: The materials that allow current to flow through them are called conductors. The materials that have low resistivity will be a better conductor.

Use the data in the table to answer the following – Table shows electrical resistivity of some substances at 20 ° C . Substances Material Resistivity (Ω m) Conductors Silver 1 . 60 × 10 – 8 Copper 1 . 62 × 10 – 8 Aluminium 2 . 63 × 10 – 8 Tungsten 5 . 20 × 10 – 8 Nickel 6 . 84 × 10 – 8 Iron 10 . 0 × 10 – 8 Chromium 12 . 9 × 10 – 8 Mercury 94 . 0 × 10 – 8 Manganese 1 . 84 × 10 – 6 Alloys Constantan (alloy of Cu and Ni ) 49 × 10 – 6 Manganin(alloy of Cu , Mn and Ni ) 44 × 10 – 6 Nichrome (alloy of Ni , Cr , Mn and Fe ) 100 × 10 – 6 Insulators Glass 10 10 – 10 14 Hard rubber 10 13 – 10 16 Ebonite 10 15 – 10 17 Diamond 10 12 – 10 13 Paper (dry) 10 12 Which is the best conductor?

From the table, silver (with resistivity 1 . 60 × 10 - 8 Ω m ) has the lowest resistivity and is the best conductor compared to other materials given. Note: The materials that allow current to flow through them are called conductors. The materials that have low resistivity will be a better conductor.

Two lamps, one rated 100 W at 220 V , and the other 60 W at 220 V , are connected in parallel to the electric mains supply. What current is drawn from the line if the supply voltage is 220 V ?

Given, Rated power of first bulb, P 1 = 100 W and Rated voltage, V = 220 V Rated power of second bulb, P 2 = 60 W and Rated voltage, V = 220 V Resistance of the first lamp , R 1 = V 2 P 1 = 220 2 100 = 484 Ω Resistance of the second lamp, R 2 = V 2 P 2 = 220 2 60 = 806 . 67 Ω If these two resistors are joined in parallel, equivalent resistance, R e q = 484 × 806 . 67 484 + 806 . 67 Current drawn from the line , I = V R e q ⇒ I = 220 484 × 806 . 67 484 + 806 . 67 = 220 302 . 5 = 0 . 727 A

How much energy is given to each coulomb of charge passing through a 6 V battery?

The potential difference created by battery, ∆ V = 6 V The potential difference between two points in a circuit is defined as the energy required (or work done) in moving one coulomb of charge from one point to the other. ∆ V = W q , where W is work done by battery and q is the charge. ⇒ W = Δ V × q = 6 V × 1 C = 6 J

Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value What change will occur in the current through it

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IMPORTANT

SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 4

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

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SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 5

Use the data in the table to answer the following –

Table shows electrical resistivity of some substances at $20 ° C$ .

Substances	Material	Resistivity (Ω m)
Conductors	Silver	$1.60 \times 10^{- 8}$
	Copper	$1.62 \times 10^{- 8}$
	Aluminium	$2.63 \times 10^{- 8}$
	Tungsten	$5.20 \times 10^{- 8}$
	Nickel	$6.84 \times 10^{- 8}$
	Iron	$10.0 \times 10^{- 8}$
	Chromium	$12.9 \times 10^{- 8}$
	Mercury	$94.0 \times 10^{- 8}$
	Manganese	$1.84 \times 10^{- 6}$
Alloys	Constantan (alloy of $Cu$ and $Ni$ )	$49 \times 10^{- 6}$
	Manganin(alloy of $Cu, Mn$ and $Ni$ )	$44 \times 10^{- 6}$
	Nichrome (alloy of $Ni, Cr, Mn$ and $Fe$ )	$100 \times 10^{- 6}$
Insulators	Glass	$10^{10} - 10^{14}$
	Hard rubber	$10^{13} - 10^{16}$
	Ebonite	$10^{15} - 10^{17}$
	Diamond	$10^{12} - 10^{13}$
	Paper (dry)	$10^{12}$

Which among iron and mercury is a better conductor?

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SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 5

Use the data in the table to answer the following –

Table shows electrical resistivity of some substances at $20 ° C$ .

Substances	Material	Resistivity (Ω m)
Conductors	Silver	$1.60 \times 10^{- 8}$
	Copper	$1.62 \times 10^{- 8}$
	Aluminium	$2.63 \times 10^{- 8}$
	Tungsten	$5.20 \times 10^{- 8}$
	Nickel	$6.84 \times 10^{- 8}$
	Iron	$10.0 \times 10^{- 8}$
	Chromium	$12.9 \times 10^{- 8}$
	Mercury	$94.0 \times 10^{- 8}$
	Manganese	$1.84 \times 10^{- 6}$
Alloys	Constantan (alloy of $Cu$ and $Ni$ )	$49 \times 10^{- 6}$
	Manganin(alloy of $Cu, Mn$ and $Ni$ )	$44 \times 10^{- 6}$
	Nichrome (alloy of $Ni, Cr, Mn$ and $Fe$ )	$100 \times 10^{- 6}$
Insulators	Glass	$10^{10} - 10^{14}$
	Hard rubber	$10^{13} - 10^{16}$
	Ebonite	$10^{15} - 10^{17}$
	Diamond	$10^{12} - 10^{13}$
	Paper (dry)	$10^{12}$

Which is the best conductor?

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IMPORTANT

SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 1

Draw a schematic diagram of a circuit consisting of a battery of three cells of

2 V

each, a

5 Ω

resistor, an

8 Ω

resistor, and a

12 Ω

resistor, and a plug key, all connected in series.

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SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 2

In a schematic diagram of a circuit consisting of a battery of three cells of

2 V

each, a

5 Ω

resistor, an

8 Ω

resistor, and a

12 Ω

resistor, and a plug key, all connected in series, put an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the

12 Ω

resistor. What would be the readings in the ammeter and the voltmeter?

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SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 1

Judge the equivalent resistance when the following are connected in parallel

1 Ω

and

10^{6} Ω

.

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SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 1

Judge the equivalent resistance when the following are connected in parallel –
$1 Ω$ , $10^{3} Ω$ and $10^{6} Ω$ .

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IMPORTANT

SCIENCE TEXTBOOK FOR CLASS X>Chapter 12 - Electricity>QUESTIONS>Q 2

An electric lamp of

100 Ω

, a toaster of resistance

50 Ω

, and a water filter of resistance

500 Ω

are connected in parallel to a

220 V

source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?

Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?

Important Questions on Electricity

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