# Q. A current loop, having two circular arcs joined by two radial lines is shown in the figure. It carries a current of 10 A. The magnetic field at point O will be close to :

JEE Main JEE Main 2019

Solution:

## $\vec{B} = \frac{\mu_{0} i}{4\pi} \theta \left[ \frac{1}{r_{1} } - \frac{1}{r_{2}}\right]\hat{k}$ $r_{1} = 3cm = 3 \times10^{-2}m$ $r_{2} = 5 cm = 5 \times10^{-2} m$ $\theta= \frac{\pi}{4} , i = 10 A$ $\Rightarrow \vec{B} = \frac{4\pi \times10^{-7}}{16} \times10 \left[ \frac{1}{3\times10^{-2}} - \frac{1}{5 \times10^{-2}}\right] \hat{k}$ $\Rightarrow \left|\vec{B} \right| = \frac{\pi}{3} \times10^{-5} T$ $\approx 1 \times10^{-5} T$

You must select option to get answer and solution

## 1. The potential to which a conductor is raised, depends on ........

KCET 2005 Electrostatic Potential And Capacitance

## 2. The refractive index of a particular material is 1.67 for blue light, 1.65 for yellow light and 1.63 for red light. The dispersive power of the material is .........

KCET 2004 Electrostatic Potential And Capacitance

## 3. In a permanent magnet at room temperature

KCET 2019 Moving Charges And Magnetism

## 4. An antenna uses electromagnetic waves of frequency 5 MHz. For proper working, the size of the antenna should be

KCET 2019 Communication Systems

## 5. In the following circuit, what are P and Q?

KCET 2019 Semiconductor Electronics: Materials Devices And Simple Circuits

## 6. Two metal plates are separated by 2 cm. The potentials of the plates are − 10 V and + 30 V. The electric field between the two plates is

KCET 2019 Electrostatic Potential And Capacitance

KCET 2019 Nuclei

## 8. For a transistor amplifier, the voltage gain

KCET 2019 Semiconductor Electronics: Materials Devices And Simple Circuits

## 9. “Parsec” is the unit of

BHU 2007 Physical World, Units and Measurements

## 10. “Parsec” is the unit of

BHU 2007 Physical World, Units and Measurements