# Q. Temperature difference of $120^{\circ}C$ is maintained between two ends of a uniform rod AB of length 2L. Another bent rod PQ, of same cross section as AB and length $\frac{3L}{2}$ , is connected across AB (See figure). In steady state, temperature difference between P and Q will be close to :

JEE Main JEE Main 2019

Solution:

## $\frac{\Delta T}{R_{eq}} = I = \frac{\left(120\right)5}{8R} = \frac{120\times5}{8R}$ $\Delta T_{PQ} = \frac{120 \times5}{8R} \times\frac{3}{5}R = \frac{360}{8} = 45^{\circ}C$

You must select option to get answer and solution

## 1. An AC ammeter is used to measure current in a circuit. When a given direct current passes through the circuit, the AC ammeter reads 3 A. When another alternating current passes through the circuit, the AC ammeter reads 4 A. Then the reading of this ammeter, if DC and AC flow through the circuit simultaneously, is

AIIMS 2010 Alternating Current

## 2. Assertion : Perspiration from human body helps in cooling the body Reason : A thin layer of water on the skin enhances its emissivity.

AIIMS 2006 Thermal Properties Of Matter

## 3. The speed of sound through oxygen at T K is v m$s^{-1}$. As the temperature becomes 2T and oxygen gas dissociates into atomic oxygen, the speed of sound

Manipal 2003 Electromagnetic Waves

## 4. If voltage across a bulb rated 220 volt-100 watt drops by $2.5\%$ of its rated value, the percentage of the rated value by which the power would decrease is

AIPMT 2012 Current Electricity

## 5. If the dimensions of a physical quantity are given by $\ce{M^aL^bT^c}$, then the physical quantity will be

AIPMT 2009 Physical World, Units and Measurements

## 6. There are 26 tuning forks arranged in the decreasing order of their frequencies. Each tuning fork gives 3 beats with the next. The first one is octave of the last. What is the frequency of 18th tuning fork?

BHU 2005 Electromagnetic Waves

## 7. The electric resistance of a certain wire of iron is $R$. If its length and radius are both doubled, then

JIPMER 2015 Current Electricity

## 8. A quarter horse power motor runs at a speed of 600 rpm. Assuming 40% efficiency, the work done by the motor in one rotation will be

Manipal 2009 Work, Energy And Power

## 9. A cannon of mass I 000 kg, located at the base of an inclined plane fires a shelI of mass 100 kg in a horizontal direction with a velocity 180 $kmh^{-1}$. The angle of inclination of the inclined plane with the horizontal is 45$^{\circ}$. The coefficient of friction between the cannon and the inclined plane is 0.5. The height, in metre, to which the cannon ascends the inclined plane as a result of the recoiI is (g = 10 $ms^{-1})$

EAMCET 2004 Laws Of Motion

## 10. Two charges $q_1$ and $q_2$ are placed 30 cm apart, as shown in the figure. A third charge $q_3$ is moved along the arc of a circle of radius 40cm from C to D. The change in the potential energy of the system is $\frac{q_3}{ 4 \pi \varepsilon_0}$ k. where k is

AIPMT 2005 Electrostatic Potential And Capacitance