Each atom consist of Proton, Electron and Neutron.
Proton are particles with positive charge.
Electron are particles with negative charge.
Neutron are particles with no charge.
“ Protons and Neutron are bound to form the nucleus of the atom. Electron are mobile, moving around the nucleus and can move from one nucleus to another.”
Materials that has varying conducting properties depending on the impurities and the charges present on the material.
Superconductor
Materials that become perfect conductors at extremely low temperature.
20.
State that the Force between two charges is proportional to the product of the charges and is inversely proportional to the square of the distance between them. COULOMB’ S LAW
A hydrogen atom is composed of an electron and a proton. The Bhor radius of the hydrogen atom is 5.30 x10 -11 m. Compute for the electrical force between the proton and the electron in the atom.
1. Find (a) the magnitude of an electrons electric field at 50.0 cm away from the electron. (b) if the another electron is placed at this distance, what would be the magnitude of electrostatic force between the electrons? (c) Is the force attractive or repulsive?
2. Two charges, Q 1 = +1.5 x 10 -8 C and Q 2 = +3.0 x 10 -8 C are 100 mm apart. What is the magnitude of the electric field halfway between them?
If the electric field in the region has a magnitude of 2.0 x 10 3 N/C and passing through the surface with an area 0.0214 m 2 . The area vector is oriented at an angle of 50 0 with respect to the electric field. Find the electric flux.
Given five charges of values Q 1 = Q 5 = +3.1 nC, Q 2 = Q 4 = -5.9 nC & q 3 = +3.1 nC, find the net electric flux through the Gaussian surface S shown in the figure below.
What is the electric potential at a distance of 5.29 x 10 -11 m from the proton? What is the potential energy of the electron and proton at this separation?
The work done on a 5.0 C charge is 7.5 J as it is moved from point A, where the potential difference is 2.0 V, to another point B. What is the electric potential difference between points A and points B? What is the potential at point B?
The plates of a parallel-plate capacitor are 5.00 mm apart and 2.00 m 2 in area. A potential difference of 10,000 volts is applied across the capacitor. Compute the capacitance, the charge on the plate and the magnitude of the electric field in the space between them.
Ratio between the capacitance of a capacitor when a dielectric material is present ( C ) and its capacitance when the space between its plate is a vacuum ( C 0 )
Where: k = dielectric constant C = Capacitance if there is dielectric C 0 = capacitance without dielectric
The parallel plates of a capacitor have an area of 2.00 x 10 -1 m 2 and have a separation distance of 1.00 x 10 -2 m and are connected to 3000 volts power supply.
The capacitor is then disconnected from the supply, and an dielectric is inserted between the plates, Find that the potential difference decreases to 1000 volts while the charge on each plate remain constant.
Two capacitors one is 491 µF and the other is 30 µF are connected in series across a 12 volts battery. Find the equivalent capacitance of the combination, the charge on each capacitor and the potential difference across it.
Two capacitor one is 5 F and the other 2 F are connected in parallel across a 100 volts battery. Find the equivalent capacitance of the combination, the charge of each and the potential difference on each capacitor.
A conductor connected to a dry cell or battery has the necessary electric potential to influence the flow of charges towards one direction, hence producing current.
Battery + - Conductor Charges Direction of charges
These positive charges are not actual particles. They are called holes , vacant spaces where there should be an electron. The charge of a hole is +1.6 x 10 -19 C .
Electrons are known as negative charge carriers . Holes are known as positive charge carriers .
Current per unit of cross-sectional area of a conductor.
A vector quantity with the same direction as the motion of positive charge carriers.
Where: I = electric current (A) J = current density (A/m 2 ) n = charge concentration v d = drift velocity (m/s) e = charge of electron A = cross-sectional area of conductor(m 2 )
A 491 gauge copper wire has a nominal diameter of 0.64 mm. This wire carries a constant current of 1.67 A to a 4,910 watts lamp. The density of free electron is 8.5 x 10 28 electrons/m 3 . Find the current density and the magnitude of drift velocity.
Property of the conducting medium that weakens the transmission of electric current.
Denoted as R and its unit is Ohm ( Ω ) .
Where: R = Resistance (Ohm, Ω ) ρ = resistivity ( Ω m) L = Length of the wire (m) A = cross-sectional area of a wire(m 2 )
105.
0.0038 1.6 x 10-8 Silver 0.0036 11 x 10-8 Platinum 0.00088 98 x 10-8 Mercury 0.0043 21 x 10-8 Lead 0.005 12 x 10-8 Iron 0.0039 1.7 x 10-8 Copper 0.0039 2.6 x 10-8 Aluminum α (k -1 ) ρ (Ω.m) Substance and their temperature coefficient. Approximate resistivities (at 20 0 C)
Measure by placing the material between two plates with constant electric field ( E ) and taking the ratio of electric field and current density ( J ) .
Varies with temperature
Where: ρ = resistivity ( Ω m) E = electric field (N/c) J = current density (A/m 2 )
Where: ρ = resistivity ( Ω m) ρ 0 = resistivity at room temperature ( Ω m) T = temperature (Kelvin,K) T 0 = room temperature (K) α = coefficient of resistivity (K -1 )
What is the resistivity of iron at 200K? Use the values of resistivity (at room temperature) and temperature coefficient of the resistivity in the handout.
The current I (Ampere, A) is directly proportional to the potential difference V (Volt,V) with resistance R (ohms, Ω ) as the proportionality constant.
Resistors R 1 = 2.00 ohms, R 2 = 3.00 ohms and R 3 = 4.00 ohms are in series connection with a voltage source of 100.0 volts. Find the equivalent resistance, electric current and electric potential difference.
Resistors R 1 = 3.00 ohms, R 2 = 5.00 ohms and R 3 = 7.00 ohms are in parallel connection with a voltage source of 110.0 volts. Find the equivalent resistance, electric current and electric potential difference.
At any point in a circuit, the sum of the currents leaving the junction point is equal to the sum of all the current entering the junction point. (Using current direction).
R 2 + ε 1 + - R 1 + ε 2 + - R 3 Junction point I 1 I 3 I 2 +
R + - C S 1 S 2 ε + - Where: ε = Batteries (Emf) S 1 & S 2 = Switches R = Resistor C = Capacitor Open Close
149.
Charging a capacitor R + - C S 1 S 2 ε + - I I I I I closed open Where: V R = Potential difference across the resistor. V C = Potential difference across the capacitor. I
A resistor with resistance R=1.0 x 10 6 Ω , capacitor with capacitance C=2.2 x 10 -6 F, a voltage source with ε = 100 v, and a switch are all connected in a single loop series circuit. The switch is initially open. When the switch is closed, calculate:
Grasp the wire with your right hand so that your thumb point in the direction of the current. The curled fingers of that hand point the direction of the magnetic field.
Current loop:
Grasp the loop so that the curled fingers of your hand point in the direction of the current; the thumb of that hand then point in the direction of the magnetic field.
A wire 0.10 m long carrying a current of 2.0 A is at 30 0 angle with respect to the magnetic field. If the magnetic field strength is 0.20 T, what is the magnitude of the force on the wire?
Magnetic north pole is located somewhere in the Greenland, near but not exactly in the same location as geographic north pole. Magnetic south pole is at its direct opposite.
Earth is the giant magnet that generates magnetic field. It enables compasses to work.
Earth magnetic north pole is actually the “south pole”, where magnetic field terminates, and the magnetic south pole is actually the “north pole” from where the magnetic field emanates.
If a charge is moving relative to a point, the electric field at that point due to the charge is changing. This on-going change generates magnetic field.
Note:
Charging Electric field generates magnetic fields.
What is the magnitude of the magnetic field 6.1 m below a power line in which there is a steady current of 100 A?
Field along a solenoid:
A solenoid of length 30.0 cm and radius 2.0 cm is closely winded with 200 turns of wire. The current in the winding is 5.0 A. Compute the magnetic field magnitude at a point near the center of the solenoid.
Atoms are like tiny magnets. The electrons form a microscopic loop.
Moving electrons generate magnetic field. Hence, atoms are like small magnets.
Most objects do not generate magnetic field despite being made-up of atoms because the atoms are oriented randomly: the atoms cancel each other’s magnetic field.
A single loop of wire with an enclosed area of 6.00 cm 2 is in a region of uniform magnetic field, with the field perpendicular to the plane of the loop. The magnetic field is decreasing at a constant rate of 0.150 T/s.
What is the induced emf ?
If the loop has a resistance of 0.300 ohms what is the current induced in the loop?
States that the induced current runs to the direction in such a way that it generates magnetic field to oppose the changes in the magnetic flux that induced the current.
Notation: the subscript that the stand for the inducing coil comes second and the subscript that stands for the coil being induced comes first.
Equation of induced emf: ε 21 is the emf induced in coil 2 due to change in current in coil 1 and ε 12 is the emf induced in coil 1 cue to change in current in coil 2.
Two single-turn coils are fixed in location such that they can induced emf to one another.
When the first coil has no current and the current in the second coil increases at rate of 15.0 A/s, the emf in the first coil is 25.0 mV. What is their mutual inductance?
When the second coil has no current and the first coil has current of 3.60 A, What is the flux linkage in the second coil?
A 160 Ω resistor, 15.0 µF capacitor and 230 mH inductor are connected to form RLC circuit with an ac generator whose conducting loop rotates at 60.0 full rotation per second and with emf amplitude of 36.0 V.
A transformer has 100 turns on its primary coil and 300 turns on the secondary coil. If the primary voltage is 110.0 V and primary current is 5.00 A. What are the secondary voltage and current?
It is the spreading of wave after it passed through a small slit.
Each point at the wavefront acts as tiny source of smaller waves called wavelets. The interference among wavelets keep wave in shape.
However, If the slit is small enough, some of the wavelets will not be able to pass through; with no interference, the wavelets from one point will be able to propagate.
Light is the electromagnetic wave that is visible to the eyes, with wavelengths between 4 x10 -7 m and 7 x10 -7 m and frequencies between 7 x 10 14 hertz and 4 x10 14 hertz.
Electric field Magnetic field Direction Wavelength
267.
Speed in a vacuum Where: c= speed of the electromagnetic waves (m/s) E=electric field (V/m) β = magnetic field (Weber/m 2 ) ε o = permitivity constant μ o = permeability constant
At a particular time the magnetic field intensity in electromagnetic wave is 2 x10 -10 Wb/m 2 . Calculate the magnitude of the electric field intensity.
The angle of incident ( θ i ) is equal to the angle of reflection ( θ r )
276.
θ i θ r θ i = 0 θ r = 0 Mirror A The light is parallel to The plane of mirror. No Reflection. Mirror B Light is reflected at an angle. θ i = θ r A B Mirror C Incident and reflected Light are both perpendicular To the plane of mirror. θ i - θ r =0 C
A light beam crosses from the vacuum to water with incident beam angle of 25.0 0 . If the index of refraction of vacuum is 1 and that of water is 1.33, what is the angle of refracted light beam?
Light from the distance is collected by a concave mirror. How far from the mirror do the light rays converge if the radius of curvature of the mirror is 200 cm.?
In order to see the image of an object in a mirror:
You must view at the image;
When you view at the image, light will come to your eyes along that line of sight.
The image location is located at that position where observers are viewing the image of an object. It is the location behind the mirror where all the light appears to diverge from.