Waves Class 10 Physics

Waves and Oscillations

• There are two types of waves: mechanical waves (require a medium to propagate) and electromagnetic waves (do not require a medium to propagate).
• Ultrasound waves are classified as longitudinal mechanical waves.
• In a transverse wave, the crests represent the highest points.
• Frequency is defined as the number of waves produced in a unit time.

LC Oscillators

• The main components of an LC oscillator are an inductive coil and a capacitor.
• In an LC oscillator, energy is stored differently in the capacitor and inductive coil: capacitor stores energy in an electric field, while the inductive coil stores energy in a magnetic field.
• The quality or Q-factor of the circuit determines the amount of damping in an LC circuit.
• In a LC tank circuit, resonance occurs when capacitive and inductive reactance are equal.

Magnetostriction Ultrasonic Generators

• The strength of the magnetic field affects the change in length of a ferromagnetic rod in a magnetostriction ultrasonic generator.
• Resonance is achieved in a magnetostriction ultrasonic generator by matching the frequency of the vibrating rod with the circuit frequency.
• An advantage of a magnetostriction ultrasonic generator is that it is easily available and inexpensive.

Piezoelectric Ultrasonic Generators

• A piezoelectric crystal produces an alternating potential difference while receiving ultrasound.
• Using a quartz crystal makes a piezoelectric oscillator more efficient by increasing stability in frequency.

Therapeutic Ultrasound

• The general range for therapeutic ultrasound intensity levels is 0.1-3.0 W/cm2.
• When the ultrasound amplitude is doubled, the energy delivered to the patient is quadrupled.
• The Doppler effect is primarily related to frequency and pitch in sound waves.
• Increasing the relative intensity by 3dB corresponds to a doubling of the absolute intensity.
• The Fraunhofer zone is characterized by a regular sonic field due to insignificant path length differences.
• The unit of power for ultrasound beams is Joule/second.
• Therapeutic shock waves are distinct from ultrasound in terms of wave behavior, with shock waves being more intense and faster.

Electric Charge and Electric Field

• Electric charge is quantized, meaning it comes in discrete packets.
• Coulomb's law states that the force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the separation between the charges.
• The electric field at a point is the amount of electric force acting on a positive test charge at that point.
• Electric flux is the measure of electric field lines penetrating normally on unit area of this surface.

Circuits and Resistance

• The unit of potential difference in a circuit is Volt.
• The frequency of a wave with a periodic time of 0.02 seconds is 50 Hz.
• The Peak-to-peak value measures the difference between the lowest negative amplitude and the highest positive amplitude on both sides.
• The Root-Mean-Square (RMS) value is used to relate the amount of AC to DC values for the heating effect.
• According to Ohm's Law, voltage (V), current (I), and resistance (R) are related by V=IxR.

Capacitors

• The unit of capacitance for a capacitor is Farads.
• Coulombic repulsion limits the addition of more charge on the plates of a capacitor.
• In the charging process of a capacitor, when the initial amount of charge on a capacitor is small, the voltage across the capacitor increases rapidly.
• When more charge is stored on the plates of a capacitor, the voltage across the capacitor increases more slowly.
• The equation Q = CV represents the charge stored on the plates of a capacitor.
• Increasing the surface area of plates increases the capacitance of a capacitor.

Direct Current (DC) and Alternating Current (AC)

• Direct Current (DC) is characterized by a continuous unidirectional flow of charged particles.
• Alternating Current (AC) is characterized by an intermittent (variable) bidirectional flow of charged particles.

Materials Properties

• Resilience is the ability of a material to absorb energy up to the proportional limit.
• Yield strength is a measure of a material's resistance to plastic deformation.
• Toughness is the ability of a material to absorb energy up to the fracture.
• Fatigue occurs when a material is subjected to dynamic load.
• Malleability is the ability of a material to undergo permanent compressive deformation without fracture.
• Ductility is the ability of a material to undergo permanent tensile deformation without fracture.
• Elastic modulus represents the rigidity of materials.

Mechanics

• The main difference between statics and dynamics in mechanics is that statics involves objects at rest or moving without acceleration, while dynamics involves objects in motion with acceleration.
• Kinetics is the analysis of forces causing motion.
• Kinematics is the description of the motion.

Levers

• In a first-class lever, the fulcrum is placed between the resistance and the force.
• In a second-class lever, the resistance is placed between the fulcrum and the force.
• In a third-class lever, the force is placed between the fulcrum and the resistance.
• The location of a lever's axis improves its mechanical advantage by moving the axis closer to the resistance.