Energy and Waves Practice Exam Flashcards

Comprehensive practice questions covering Energy (conservation, efficiency, circuits, sources) and Waves (properties, EM spectrum, sound, and light) based on the lecture notes.

What is the Law of Conservation of Energy?

Energy cannot be created or destroyed; it can only be transferred (moved from one place/object to another) or transformed (changed from one form to another). The total energy in a closed system remains constant.

Distinguish between energy transfer and energy transformation.

Energy transfer occurs when energy moves location but stays the same type (e.g., heat moving from a hot cup to a hand). Energy transformation is when energy changes from one form to another (e.g., chemical energy in a battery becoming electrical energy).

How is efficiency calculated in energy transfers?

$$Efficiency = \frac{\text{useful energy output}}{\text{total energy input}} \times 100\%$$

What are three ways to reduce wasted energy in machines?

1. Reducing friction through lubrication or smoother surfaces. 2. Insulation to reduce unwanted heat transfer. 3. Regular maintenance such as oiling moving parts.

What is the formula and units for Electric Current (I)?

$I = \frac{q}{t}$ where $I$ is current in amperes (A), $q$ is charge in coulombs (C), and $t$ is time in seconds (s).

What is Ohm's Law?

The voltage across a conductor is directly proportional to the current through it, provided resistance is constant: $V = IR$, where $V$ is voltage (volts), $I$ is current (amps), and $R$ is resistance (ohms).

How do Current and Voltage behave in a series circuit?

Current is the same at every point in the circuit, while Voltage splits or is shared across the components.

How do Current and Voltage behave in a parallel circuit?

Current splits across branches and adds up to the total, while Voltage is the same across each parallel branch.

What is the formula for total resistance in a series circuit?

$$R_T = R_1 + R_2 + ...$$

What is the formula for total resistance in a parallel circuit?

$$\frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2} + ...$$

Why is household wiring connected in parallel?

To ensure each appliance receives the full/same voltage and to allow other devices to keep working if one fails or is switched off.

What is the difference between AC and DC current?

AC (Alternating Current) regularly reverses direction and is used in mains household supply. DC (Direct Current) flows in one direction only and is used in batteries and electronics.

How is electrical Power (P) calculated?

$P = \frac{E}{t}$ (Power = Energy ÷ time), measured in watts (W).

What energy transformation occurs in a Photovoltaic (PV) cell?

Light energy is transformed directly into electrical energy.

Distinguish between mechanical and electromagnetic (EM) waves.

Mechanical waves require a medium (solid, liquid, or gas) to travel and cannot travel through a vacuum, whereas EM waves do not require a medium and can travel through a vacuum.

What is the difference between transverse and longitudinal waves?

In transverse waves, particle motion is perpendicular to the direction of energy transfer (e.g., light). In longitudinal waves, particle motion is parallel to the direction of energy transfer (e.g., sound).

List the Electromagnetic Spectrum in order from lowest to highest frequency.

Radio waves, Microwaves, Infrared, Visible light (ROYGBIV), Ultraviolet, X-rays, and Gamma rays.

What is the Universal Wave Equation?

$v = f\timesλ$ where $v$ is speed ($m/s$), $f$ is frequency ($Hz$), and $λ$ is wavelength ($m$).

How does Pitch relate to sound wave properties?

Pitch relates to frequency: higher frequency results in a higher pitch, and lower frequency results in a lower pitch.

Explain the Doppler Effect.

The change in observed frequency (and pitch) of a wave due to relative motion between the source and the observer. Moving toward the observer increases frequency (higher pitch); moving away decreases it (lower pitch).

Name the three bones in the middle ear and their function.

The ossicles (hammer, anvil, and stirrup) function to amplify vibrations.

What is the Law of Reflection?

The angle of incidence equals the angle of reflection, both measured from the normal (a line perpendicular to the surface).

What is refraction and why does it occur?

Refraction is the bending of light as it passes from one medium to another due to a change in the speed of light.

How do concave and convex mirrors differ in reflecting light?

Concave mirrors curve inward and converge light to a focal point. Convex mirrors curve outward and diverge light, producing a wider field of view.

What causes the dispersion of white light into a spectrum?

White light separates into component colors (ROYGBIV) when passing through a prism because each wavelength refracts by a slightly different amount.