For the circuit shown in the figure
Show Hint
\(\, \, \, \, \, \, \, p=\frac{V^2}{R} \, \, or \, \, P= V^2\)
- the current $I$ through the battery is $7.5 \,mA$
- the potential difference across $R_L$ is $18\, V$
- ratio of powers dissipated in $R_1 $ and $R_2$ is $3$
- if $R_1 $ and $ R_2$ are interchanged, magnitude of the power dissipated in $R_L$ will decrease by a factor of $9$
The Correct Option is D
Approach Solution - 1
For the circuit shown in the figure
\(R_{total = 2 + \frac{6 \, \times \, 1.5}{6 \, + \, 1.5} } = 3.2k \Omega\)
\((A) \, I = \frac{25V}{3.2k \Omega} = 7.5mA = I_{R_1}\)
\(\, \, \, \, \, \, \, \, I_{R_2} = \bigg( \frac{R_L}{ R_L + R_2} \bigg) I\)
\(\, \, \, \, \, \, \, \, \, \, I = \frac{1.5}{7.5} \times 7.5 = 1.5mA\)
\(\, \, \, \, \, \, I_{R_2} = 6mA\)
\((B)V_{R_L} = (I_{R_L}) (R_L) = 9V\)
\((C) \frac{P_{R_1}}{P_{R_2}} = \frac{(I^2_{R_1} R_1)}{(I^2_{R_2})R_2} = \frac{(7.5)^2 (2)}{(1.5)^2(6)} = \frac{25}{3}\)
(D) Now potential differences across \(R_L\) will be \(V_L = 24 \bigg[ \frac{6/7}{6 + 6/7} \bigg] = 3V\) Earlier it was 9 V
Since, \(\, \, \, \, \, \, \, p=\frac{V^2}{R} \, \, or \, \, P= V^2\)
In the new situation, the potential difference has been decreased three times. Therefore, if R1 and R2 are interchanged, magnitude of the power dissipated in RL will decrease by the factor of 9.
Discover More Topics From This Chapter: Current Electricity
Approach Solution -2
The Correct Answer is (D)
Real Life Applications
- To keep the same voltage level across all of the loads and components connected to it, a parallel circuit is employed.
- To avoid the effects of any one load harming the other as in a series circuit, a parallel circuit is utilized.
- When using a low voltage to drive several loads, a parallel circuit comes in quite handy.
Question can also be asked as
- What is the current flowing through each resistor?
- What is the voltage drop across each resistor?
- What is the total power dissipated by the circuit?
- What is the equivalent resistance of the circuit?
- What is the impedance of the circuit if it is connected to an AC source?
- What is the phase angle between the current and voltage in the circuit?
- What is the power factor of the circuit? What is the maximum current that the circuit can safely handle?
Top Questions on Current electricity
- An infinitely long straight wire carrying current $I$ is bent in a planar shape as shown in the diagram. The radius of the circular part is $r$. The magnetic field at the centre $O$ of the circular loop is :
- JEE Main - 2026
- Physics
- Current electricity
The equivalent resistance between the points \(A\) and \(B\) in the given circuit is \[ \frac{x}{5}\,\Omega. \] Find the value of \(x\).
- JEE Main - 2026
- Physics
- Current electricity
- In a meter bridge experiment to determine the value of unknown resistance, first the resistances \(2\,\Omega\) and \(3\,\Omega\) are connected in the left and right gaps of the bridge and the null point is obtained at a distance \(l\) cm from the left end. Now, when an unknown resistance \(x\,\Omega\) is connected in parallel to \(3\,\Omega\), the null point is shifted by \(10\,\text{cm}\) to the right. The value of \(x\) is ________ \(\Omega\).
- JEE Main - 2026
- Physics
- Current electricity
A Wheatstone bridge is initially at room temperature and all arms of the bridge have same value of resistances \[ (R_1=R_2=R_3=R_4). \] When \(R_3\) resistance is heated, its resistance value increases by \(10%\). The potential difference \((V_a-V_b)\) after \(R_3\) is heated is _______ V.
- JEE Main - 2026
- Physics
- Current electricity
The heat generated in 1 minute between points A and B in the given circuit, when a battery of 9 V with internal resistance of 1 \(\Omega\) is connected across these points is ______ J.
- JEE Main - 2026
- Physics
- Current electricity
Questions Asked in JEE Advanced exam
- Let $ x_0 $ be the real number such that $ e^{x_0} + x_0 = 0 $. For a given real number $ \alpha $, define $$ g(x) = \frac{3xe^x + 3x - \alpha e^x - \alpha x}{3(e^x + 1)} $$ for all real numbers $ x $. Then which one of the following statements is TRUE?
- JEE Advanced - 2025
- Fundamental Theorem of Calculus
- A linear octasaccharide (molar mass = 1024 g mol$^{-1}$) on complete hydrolysis produces three monosaccharides: ribose, 2-deoxyribose and glucose. The amount of 2-deoxyribose formed is 58.26 % (w/w) of the total amount of the monosaccharides produced in the hydrolyzed products. The number of ribose unit(s) present in one molecule of octasaccharide is _____.
Use: Molar mass (in g mol$^{-1}$): ribose = 150, 2-deoxyribose = 134, glucose = 180; Atomic mass (in amu): H = 1, O = 16- JEE Advanced - 2025
- Biomolecules
Let $ P(x_1, y_1) $ and $ Q(x_2, y_2) $ be two distinct points on the ellipse $$ \frac{x^2}{9} + \frac{y^2}{4} = 1 $$ such that $ y_1 > 0 $, and $ y_2 > 0 $. Let $ C $ denote the circle $ x^2 + y^2 = 9 $, and $ M $ be the point $ (3, 0) $. Suppose the line $ x = x_1 $ intersects $ C $ at $ R $, and the line $ x = x_2 $ intersects $ C $ at $ S $, such that the $ y $-coordinates of $ R $ and $ S $ are positive. Let $ \angle ROM = \frac{\pi}{6} $ and $ \angle SOM = \frac{\pi}{3} $, where $ O $ denotes the origin $ (0, 0) $. Let $ |XY| $ denote the length of the line segment $ XY $. Then which of the following statements is (are) TRUE?
- JEE Advanced - 2025
- Conic sections
- Adsorption of phenol from its aqueous solution on to fly ash obeys Freundlich isotherm. At a given temperature, from 10 mg g$^{-1}$ and 16 mg g$^{-1}$ aqueous phenol solutions, the concentrations of adsorbed phenol are measured to be 4 mg g$^{-1}$ and 10 mg g$^{-1}$, respectively. At this temperature, the concentration (in mg g$^{-1}$) of adsorbed phenol from 20 mg g$^{-1}$ aqueous solution of phenol will be ____. Use: $\log_{10} 2 = 0.3$
- JEE Advanced - 2025
- Adsorption
- At 300 K, an ideal dilute solution of a macromolecule exerts osmotic pressure that is expressed in terms of the height (h) of the solution (density = 1.00 g cm$^{-3}$) where h is equal to 2.00 cm. If the concentration of the dilute solution of the macromolecule is 2.00 g dm$^{-3}$, the molar mass of the macromolecule is calculated to be $X \times 10^{4}$ g mol$^{-1}$. The value of $X$ is ____. Use: Universal gas constant (R) = 8.3 J K$^{-1}$ mol$^{-1}$ and acceleration due to gravity (g) = 10 m s$^{-2}\}$
- JEE Advanced - 2025
- Colligative Properties
Concepts Used:
Current Electricity
Current electricity is defined as the flow of electrons from one section of the circuit to another.
Types of Current Electricity
There are two types of current electricity as follows:
Direct Current
The current electricity whose direction remains the same is known as direct current. Direct current is defined by the constant flow of electrons from a region of high electron density to a region of low electron density. DC is used in many household appliances and applications that involve a battery.
Alternating Current
The current electricity that is bidirectional and keeps changing the direction of the charge flow is known as alternating current. The bi-directionality is caused by a sinusoidally varying current and voltage that reverses directions, creating a periodic back-and-forth motion for the current. The electrical outlets at our homes and industries are supplied with alternating current.