A piece of copper and another of germanium are cooled from room temperature to 80 K . The resistance of...

copper decreases and germanium increases

copper increases ∧ germanium decreases

Copper and Silicon are cooled from 300 K to 60 K . The specific resistance

decreases in copper but increases in silicon

increases in copper but decreases in silicon

Constantan wire is used in making standard resistances because its

temperature coefficient of resistance is negligible

E M B I B E

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 59

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IMPORTANT

Earn 100

If $n, e, τ$ and $m$ respectively represent the electron density, relaxation time and mass of the electron, then the resistance of a wire of length $l$ and area of cross-section $A$ will be

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Important Questions on Current Electricity

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IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 60

A group of $N$ cells whose emf varies directly with the internal resistance as per the equation $E_{N} = 1.5 r_{N}$ are connected, as shown in the figure. The current $I$ in the circuit is

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 61

The current in the resistance $R$ will be zero, if

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 62

The materials of negative electrode, positive electrode, electrolyte and depolariser of dry cell are respectively

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 63

A current of

4.8 A

is flowing in a conductor. The number of electrons passing through any cross-section per second is

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 64

The quantity of charge that flows through a given cross-section in one second, when there is a steady current of one ampere is

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 65

The net resistance of an ammeter should be small to ensure that

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IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 66

Two cylindrical rods of uniform cross-sectional area

A

and

2 A

having free electrons per unit volume

2 n

and

n

, respectively, are joined in series. A current

I

flows through them in steady-state. Then, the ratio of the drift velocity of a free electron in the left rod to the drift velocity of the electron in the right rod

(\frac{V_{L}}{V_{R}})

is,

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IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 2>Q 67

Two electric bulbs, each designed to operate with a power of $500 W$ in $220 V$ lines are put in series in a $110 V$ . What will be the power generated by each bulb?