Q: On a bulb it is written \$220\ V\$ and \$60\ W\$. Find out the resistance of the bulb and the value of the current flowing through it:

\$\textbf{Step1:Resistance of bulb}\$We know,Power, \$P=\dfrac {V^2}{R}\$\$\implies R=\dfrac {V^2}{P}\$\$R=\dfrac {(220)^2}{60}\$\$R=806.67\ \Omega\$\$\textbf{Step2:Apply Ohm's law}\$According to Ohm's law,\$V=IR\$\$\implies I=\dfrac {V}{R}\$\$I=\dfrac {220}{806.67}\$\$I=0.27\ A\$

Q: A circular conductor is made of a uniform wire of resistance 2 x \$10^{-3}\$ ohm/metre and the diameter of this circular conductor is 2 metres. Then the resistance measured between the ends of the diameter is (in ohms)

The resistance per unit length is given to be \$ R' = 2 \times 10^{-3} \$The length can be calculated as \$ L = \pi \times D \$, where D is given diameter of 2 m. Hence \$ L = 2 \pi \$Therefore,Resistance \$ = 2 \times 10^{-3} \times 2\pi = 4 \pi \times 10^{-3} Ohms. \$Now when the resistance is measured between ends of any diameter, it can be seen as parallel connection of two resistances R/2 each (R being the total resistance of the entire loop). So the resistance between two end points of a diameter will be R/4 i.e. \$\pi \times 10^{-3} Ohms. \$

Question 1

In the network shown, each resistance is equal to R. The equivalentresistance between diagonally opposite corners is:

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Question 2

On a bulb it is written $220\ V$ and $60\ W$. Find out the resistance of the bulb and the value of the current flowing through it:

Accepted Answer

$\textbf{Step1:Resistance of bulb}$We know,Power, $P=\dfrac {V^2}{R}$$\implies R=\dfrac {V^2}{P}$$R=\dfrac {(220)^2}{60}$$R=806.67\ \Omega$$\textbf{Step2:Apply Ohm's law}$According to Ohm's law,$V=IR$$\implies I=\dfrac {V}{R}$$I=\dfrac {220}{806.67}$$I=0.27\ A$&#8203;

Question 3

1 kWh is equal to

Accepted Answer

1 kilowatt hour is the energy produced by 1 kilowatt  power source in 1 hour.$1kWh=1kW\times 1hour=1000\times 3600 W.s$$\implies 1kWh=3.6\times 10^6J$$\implies 1kWh=3.6MJ$Answer-(D)

Question 4

A fuse wire of radius 0.1 mm melts when a current(in A) of 10 A is passed through it. Find the current at which a fuse wire of 0.12 mm will melt.

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Question 5

An electric lamp whose resistance of 10 ohm, and a conductor of 2 ohm resistance are connected in series with a 6 V battery. The total current through the circuit and the potential difference across the electric lamp are :

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Question 6

If the filament of bulb D breaks then does bulb C give more light, less light, the same light or no light?

Accepted Answer

It is assumed that every bulb is identical and has same resistance($R$).So C and D are in parallel.And A , B and combination of (C and D) all these three are in series.Initially resistance here was $R/2$ (C and D both have $R$ in parallel).So resistances in series are $R$ ,$R$ and $R/2$. Since resistance across third element is less than first two elements so less portion of cell voltage will be shared here.Now bulb D breaks.So combination of C and D will reduced to only C.Now only C is there so net resistance here is $R$ .So now A ($R$ resistance) , B ($R$ resistance) and C ($R$ resistance) are in series and have equal resistances so voltage across C will be $1/3$ of cell voltage.In other words after breaking of D voltage across C has increased from before hence it will glow more brightly than before.

Question 7

Do the arrows in the diagram indicate the direction of electron flow or conventional flow of electricity?

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We know that conventional current flows from positive terminal of battery or cell to negative terminal of cell.Since in the figure the current is shown from positive terminal of cell (represented by bigger line) hence it is conventional current shown in the figure.Direction of electron flow is opposite to conventional current direction.

Question 8

The $I-V$ graphs for two different electrical appliances $A$ and $B$ are as shown in the diagram. If $R_A$ and $R_B$ are the resistance of the devices, then

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Question 9

A circular conductor is made of a uniform wire of resistance 2 x $1 0^{- 3}$ ohm/metre and the diameter of this circular conductor is 2 metres. Then the resistance measured between the ends of the diameter is (in ohms)

Accepted Answer

The resistance per unit length is given to be $ R' = 2 \times 10^{-3} $The length can be calculated as $ L = \pi \times D $, where D is given diameter of 2 m. Hence $ L = 2 \pi $Therefore,Resistance $ = 2 \times 10^{-3} \times 2\pi = 4 \pi \times 10^{-3}  Ohms. $Now when the resistance is measured between ends of any diameter, it can be seen as parallel connection of two resistances R/2 each (R being the total resistance of the entire loop). So the resistance between two end points of a diameter will be R/4 i.e. $\pi \times 10^{-3}  Ohms. $

Question 10

Identify the cases where the bulbs are connected totally in series.

Accepted Answer

A series connection is one in which all elements are in the same branch or the same wire goes through all the elements. So clearly only in option A and D all bulbs are in the same branch hence they are totally in series.So option A and D are correct.

Electricity

Physics
8666 Views

In the network shown, each resistance is equal to R. The equivalent
resistance between diagonally opposite corners is:

On a bulb it is written $220 V$ and $60 W$ . Find out the resistance of the bulb and the value of the current flowing through it:

1 kWh is equal to

A fuse wire of radius 0.1 mm melts when a current(in A) of 10 A is passed through it. Find the current at which a fuse wire of 0.12 mm will melt.

An electric lamp whose resistance of 10 ohm, and a conductor of 2 ohm resistance are connected in series with a 6 V battery. The total current through the circuit and the potential difference across the electric lamp are :

If the filament of bulb D breaks then does bulb C give more light, less light, the same light or no light?

Do the arrows in the diagram indicate the direction of electron flow or conventional flow of electricity?

The $I - V$ graphs for two different electrical appliances $A$ and $B$ are as shown in the diagram. If $R_{A}$ and $R_{B}$ are the resistance of the devices, then

A circular conductor is made of a uniform wire of resistance 2 x $1 0^{- 3}$ ohm/metre and the diameter of this circular conductor is 2 metres. Then the resistance measured between the ends of the diameter is (in ohms)

Identify the cases where the bulbs are connected totally in series.

Electricity

Physics 8666 Views

In the network shown, each resistance is equal to R. The equivalent resistance between diagonally opposite corners is:

On a bulb it is written 220 V and 60 W. Find out the resistance of the bulb and the value of the current flowing through it:

1 kWh is equal to

A fuse wire of radius 0.1 mm melts when a current(in A) of 10 A is passed through it. Find the current at which a fuse wire of 0.12 mm will melt.

An electric lamp whose resistance of 10 ohm, and a conductor of 2 ohm resistance are connected in series with a 6 V battery. The total current through the circuit and the potential difference across the electric lamp are :

If the filament of bulb D breaks then does bulb C give more light, less light, the same light or no light?

Do the arrows in the diagram indicate the direction of electron flow or conventional flow of electricity?

The I−V graphs for two different electrical appliances A and B are as shown in the diagram. If RA​ and RB​ are the resistance of the devices, then

A circular conductor is made of a uniform wire of resistance 2 x 10−3 ohm/metre and the diameter of this circular conductor is 2 metres. Then the resistance measured between the ends of the diameter is (in ohms)

Identify the cases where the bulbs are connected totally in series.

Physics
8666 Views

In the network shown, each resistance is equal to R. The equivalent
resistance between diagonally opposite corners is:

On a bulb it is written $220 V$ and $60 W$ . Find out the resistance of the bulb and the value of the current flowing through it:

The $I - V$ graphs for two different electrical appliances $A$ and $B$ are as shown in the diagram. If $R_{A}$ and $R_{B}$ are the resistance of the devices, then

A circular conductor is made of a uniform wire of resistance 2 x $1 0^{- 3}$ ohm/metre and the diameter of this circular conductor is 2 metres. Then the resistance measured between the ends of the diameter is (in ohms)