Physics Current Electricity

A resistor develops 300 J of thermal energy in 15s, when a current of 2 A is passed through it. If the current increases to 3 A, the energy developed in 10s is…………….J.

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Contributor-Level 9

$H = I^{2} R t = 2^{2} * R * 15$

$\Rightarrow 300 = 60 R$

$R = 5 Ω$

Now for 3A, time = 10 sec

$H' = l^{2} R t = 3^{2} * 5 * 10 = 450 J$

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11 months ago

A current through a wire-depends on time as

i = a₀t + bt²

Where a₀ = 20A/s and b = 8As^-². Find the charge crossed through a section of the wire in 15s.

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Contributor-Level 10

$\frac{d q}{d t} = t = 20 t + 8 t^{2}$

$\Rightarrow \int_{0}^{q} d q = \int_{0}^{15} (20 t + 8 t^{2}) d t$

$\Rightarrow q = 20 * \frac{1 5^{2}}{2} + 8 . \frac{1 5^{3}}{3} = 11250 C$

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11 months ago

A cell E₁ of emf 6V and internal resistance $2 Ω$ is connected with another cell E₂ of emf 4V and internal resistance $8 Ω$ (as shown in the figure). The potential difference across points X and Y is:

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Contributor-Level 10

$i = \frac{6 - 4}{2 + 8} = 0.2 A$

$V_{x} + 4 + 0.2 * 8 = V_{Y}$

$\Rightarrow V_{Y} - V_{X} = 5.6 V$

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11 months ago

A teacher in his physics laboratory allotted an experiment ot determine the resistance (G) of a galvanometer. Students took the observations for $\frac{1}{3}$ $\frac{}{}$ deflection in the galvanometer. Which of the below is true for measuring value of G?

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Contributor-Level 9

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11 months ago

In the colour coding system of carbon resistors, the tolerance (in %) shown by gold band is ______.

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Vishal Baghel

Contributor-Level 10

Gold band is equal to 5% tolerance

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11 months ago

A multi range current ammeter can be constructed by using a galvanometer circuit as shown in figure. We want a current meter that can measure 10 mA, 100 mA and 1A using a galvanometer of resistance 10 Ω and that produces maximum deflection for current 1 mA. Value of S₁ + S₂ + S₃ in ohms is

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Vishal Baghel

Contributor-Level 10

IgRc = (I - Ig) (S? + S? + S? )
1mA * 10 = 9mA (S? + S? + S? )

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11 months ago

10 resistors, each of resistance R are connected in series to a battery of emf E and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased n times. The value of n is:

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Contributor-Level 9

$i_{series} = \frac{E}{R_{series}}$

$\Rightarrow i_{series} = \frac{E}{10 R}$

$i_{parallel} = \frac{E}{R_{Parallel}}$

$= \frac{E}{R / 10}$

$i_{parallel} = n * i_{series}$

$\Rightarrow \frac{10 E}{R} = \frac{n E}{10 R}$

$\Rightarrow n = 100$

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11 months ago

The resistance of platinum wire at $0^{?} C$ is $2 Ω$ and $6.8 Ω$ at $80^{?} C$ . The temperature coefficient of resistance of the wire is:

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Contributor-Level 9

$R = R_{0} (1 + α Δ T)$

$\begin{array}{r} \Rightarrow 6.8 = 2 [1 + α * (80 - 0)] \\ \Rightarrow α = \frac{3.4 - 1}{80} \\ = 0.03 \\ = 3 * 10^{- 2}^{?} C^{- 1} \end{array}$

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11 months ago

Three resistors having resistances r₁,r₂ and r₃ are connected as shown in the given circuit. The ratio i₂/i₃ of currents in terms of resistances used in the circuit is:

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Contributor-Level 10

V = ir
i = V/r
i = (1/r) [v is same for r? & r? ]
i? /i? = r? /r?
i? = (r? / (r? +r? )i?
i? /i? = r? / (r? +r? )

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11 months ago

The effective resistance of a parallel connection that consists of four wires of equal length, equal area of cross-section and same material is 0.25Ω. What will be the effective resistance if they are connected in series?

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