Physics · Unit 2 · 5 hrs
Electric and Magnetic Field
Exam-focused notes for Electric and Magnetic Field (Physics, PHY118): what the TU syllabus asks and how it has actually been tested, with 16 solved past questions from this unit.
What this unit covers
- Electric and magnetic field and potential
- Force on current carrying wire
- magnetic dipole moment
- Force on a moving charge
- Hall effect
- Electromagnetic waves
Force on current carrying wire
Describe torque on a current-carrying rectangular loop of wire on a pivot rod when placed in a magnetic field. Give alternative way of increasing the torque on the coil.[10]
Consider a rectangular loop of wire ABCD of dimensions a × b (width × length), carrying current I, mounted on a pivot rod (axis of rotation), and placed in a uniform external magnetic field B. Let the plane of the loop make an angle φ with the magnetic fiel...
Full solved answer →Explain the effect of external magnetic field on current carrying loops. Describe torque on a current-carrying rectangular loop of wire on a pivot rod when placed in a magnetic field. Give alternative way of increasing the torque on the coil.[10]
When a current-carrying loop is placed in an external magnetic field, the magnetic field exerts forces on the current-carrying sides of the loop. These forces do not necessarily cancel each other out as a net force, but they can produce a net torque that te...
Full solved answer →Find expression for force on a current-carrying wire in a magnetic field to find the force experienced by a single charge.[10]
Consider a straight conductor of: - Length l - Cross-sectional area A - Placed in a uniform magnetic field of intensity B - Making an angle θ with the direction of the magnetic field The conductor contains free electrons (charge carriers) moving with drift ...
Full solved answer →Force on a moving charge
A proton is accelerated through a potential difference of 200 V. It then enters a region where there is a magnetic field B = 0.5 T. The magnetic field is perpendicular to the direction of motion of the proton. Find the force experienced by the proton. [5]
Quantity Value ------ Potential difference $V = 200$ V Magnetic field $B = 0.5$ T Angle between $\vec{v}$ and $\vec{B}$ $\theta = 90°$ Proton charge $q = e = 1.6 \times 10^{-19}$ C Proton mass $m = 1.67 \times 10^{-27}$ kg Energy conservation: $$qV = \frac{...
Full solved answer →A proton is moving with a velocity $\vec{v} = (3 \times 10^5 \hat{i} + 7 \times 10^5 \hat{k})$ m/sec in a region where there is a magnetic field $\vec{B} = 0.4 \hat{j}$ T. Find the force experienced by the proton. [5]
Quantity Value ------ Charge of proton $q = 1.6 \times 10^{-19}$ C Velocity $\vec{v} = (3 \times 10^5\,\hat{i} + 7 \times 10^5\,\hat{k})$ m/s Magnetic field $\vec{B} = 0.4\,\hat{j}$ T The magnetic force is: $$\vec{F} = q(\vec{v} \times \vec{B})$$ Cross prod...
Full solved answer →Electromagnetic waves
How electric and magnetic fields are incorporated in electromagnetic wave? Explain. [5]
Maxwell showed that any oscillating charge distribution produces electric (E) and magnetic (B) fields that travel together through space as an electromagnetic wave with speed 3 × 10⁸ m/s. --- When an electromagnetic wave travels along the x-axis: - The Elec...
Full solved answer →Electric and magnetic field and potential
A potential difference of 100 V is applied between the two plates one being at the high potential. An alpha particle of charge $q=3.2\times 10^{-19}$ C is released from one plate to another plate. What will be the velocity of the alpha-particle when it reaches the plate? The mass of the alpha particle is $6.70\times 10^{-19}$ kg. [5]
Quantity Value ------ Potential difference $V = 100 \text{ V}$ Charge of alpha particle $q = 3.2 \times 10^{-19} \text{ C}$ Mass of alpha particle $m = 6.70 \times 10^{-27} \text{ kg}$ Initial velocity $u = 0$ (released from rest) Note on data: The question...
Full solved answer →A potential difference of 100 V is established between the two plates one being the high potential plate (say A). A proton of charge $q=1.6\times 10^{-19}$ C is released from plate B, the another plate. What will be the velocity of the proton when it reaches plate A? The mass of the proton is $1.67\times 10^{-27}$ kg. [5]
Quantity Value ------ Potential difference $V = 100$ V Charge of proton $q = 1.6 \times 10^{-19}$ C Mass of proton $m = 1.67 \times 10^{-27}$ kg Initial velocity $u = 0$ (released from rest) Plate A is the high-potential plate; proton released from plate B ...
Full solved answer →Two large parallel plates are separated by a distance of 5 cm. The plates have equal but opposite charges that create an electric field in the region between the plates. An α particle (q = $3.2 \times 10^{-27}$ kg) is released from the positively charged plate, and strikes the negatively charged plate $2 \times 10^{-6}$ sec. later. Assuming that the electric field between the plates is uniform and perpendicular to the plates, what is the strength of the electric field? [5]
Quantity Value ------ Plate separation $d = 5 \text{ cm} = 0.05 \text{ m}$ Mass of α-particle $m = 6.68 \times 10^{-27} \text{ kg}$ (standard value) Charge of α-particle $q = 3.2 \times 10^{-19} \text{ C}$ (standard value) Time to cross gap $t = 2 \times 10...
Full solved answer →An electron is placed midway between two fixed charges, $q_1 = 2.5 \times 10^{-10}$ C and $q_2 = 5 \times 10^{-10}$ C. If the charges are 1 m apart, what is the velocity of the electron when it reaches a point 10 cm from $q_2$? [5]
- $q1 = 2.5 \times 10^{-10}$ C - $q2 = 5.0 \times 10^{-10}$ C - Separation $d = 1$ m - Initial position: midway, i.e. $0.5$ m from each charge - Final position: $10$ cm $= 0.1$ m from $q2$, hence $0.9$ m from $q1$ - Electron mass $me = 9.11 \times 10^{-31}$...
Full solved answer →Hall effect
A current of 50 A is supplied in a slab of copper 0.5 cm thick and 2 cm wide which is placed in a magnetic field $B$ of 1.5 T. The magnetic field is perpendicular to the plane of the slab and to the current. If the free electron concentration in copper is $8.4 \times 10^{28} \text{ electrons/m}^3$, what will be the magnitude of the Hall voltage across the width of the slab? [5]
Quantity Value ------ Current, $I$ $50\ \text{A}$ Thickness of slab, $t$ $0.5\ \text{cm} = 0.5 \times 10^{-2}\ \text{m}$ Width of slab, $w$ $2\ \text{cm} = 2 \times 10^{-2}\ \text{m}$ Magnetic field, $B$ $1.5\ \text{T}$ (perpendicular to plane of slab and t...
Full solved answer →Describe behavior of mobile negative charges in the Hall effect experiment. [5]
The Hall Effect is the phenomenon of development of a transverse electric field (and hence a transverse voltage) across a current-carrying conductor when it is placed in a perpendicular magnetic field. --- Consider a rectangular conducting strip carrying cu...
Full solved answer →Explain Hall effect and discuss the importance of Hall voltage while manufacturing electronic devices. [5]
The Hall Effect is the phenomenon in which a transverse electric field (and hence a potential difference) is developed across a current-carrying conductor when it is placed in a magnetic field perpendicular to the direction of current flow. Consider a recta...
Full solved answer →A current of 50 A is established in a slab of copper 0.5 cm thick and 2 cm wide. The slab is placed in a magnetic field B of 1.5 T. The magnetic field is perpendicular to the plane of the slab and to the current. The free electron concentration in copper is $8.4 \times 10^{28}$ electrons/m³. What will be the magnitude of the Hall voltage across the width of the slab? [5]
Quantity Value ------ Current, $I$ $50\ \text{A}$ Thickness, $t$ $0.5\ \text{cm} = 0.5\times10^{-2}\ \text{m}$ Width, $w$ $2\ \text{cm} = 2\times10^{-2}\ \text{m}$ Magnetic field, $B$ $1.5\ \text{T}$ Electron concentration, $n$ $8.4\times10^{28}\ \text{m}^{...
Full solved answer →magnetic dipole moment
Discuss magnetic dipole moment. What is its effect on atom and on molecules? Explain. [5]
A magnetic dipole moment is a measure of the strength of a magnetic dipole (a tiny current loop or a spinning charged particle). It is defined as the product of the current flowing in a loop and the area enclosed by that loop. $$\vec{\mu} = I \cdot \vec{A}$...
Full solved answer →Discuss magnetic dipole moment. What is its effect on atom and on molecules? Explain.[5]
A magnetic dipole moment is a measure of the strength of a magnetic dipole (a tiny current loop or a spinning charged particle). It is defined as the product of the current flowing in a loop and the area enclosed by that loop. $$\vec{\mu} = I \cdot \vec{A}$...
Full solved answer →Make Unit 2 stick
Practice PHY118 with flashcards & quizzes