Physics 2/

Tentative Schedule

• The tentative schedule indicates that the exam will occur on April 16.

• Information is verified and sent by the university.

Group Work Activity

• Group work is an in-class activity that is designed to be straightforward and collaborative.

• Students work together to develop answers and fill out a survey.

• Attendance in class is emphasized for successful participation and understanding of the course material.

Concerns about Participation

• It was noted that a third of the students did not engage in the previous survey, which raises concerns about overall participation.

• The course have varying levels of difficulty, ranging from easy to extremely challenging.

• Encouragement for students to attend class and ask questions to succeed in the course, particularly in mathematics.

Examination Guidelines

• Students are required to use only a basic calculator, not an internet-connected device.

• The calculator should have capabilities such as basic functions and trigonometric calculations (e.g., sine, cosine, square roots).

• No storage of equations in calculators is allowed, though some equations will be provided during the test.

Survey and Calculations

• Discussion of a problem where the group calculated a velocity:

  • Velocity derived: $128 ext{ ml/s} = 0.28 \times 10^{-3} \text{ m/s}$

  • Distance to lamp: $x = 3 ext{ m}$

  • Time calculation: $t = \frac{d}{v} = \frac{3 m}{0.28 \times 10^{-3} m/s} = 10714 ext{ s}$

• Emphasis that the activity is not a quiz but a collaborative effort to understand the material as a group.

Introduction to Electric Power

• Definition of Power:

  • Power is identified as energy divided by time, denoted mathematically as: $P = \frac{E}{t}$

• Electric Power Component:

  • Power in electric circuits can be calculated using voltage (V) and current (I):

  • Power formula: $P = V \times I$

  • Discussion of the physical meaning behind various terms and calculations in power.

Ohm's Law

• Ohm's Law summarized:

  • Formula: $V = I \times R$

  • This law applies in circuits where the resistance (R) remains constant.

• Variations of power equations derived from Ohm's Law:

  • From $P = V \times I$, it can yield:

  • $P = I^2 \times R$

  • $P = \frac{V^2}{R}$

Resistance and Resistivity

• Equation for resistance in relation to resistivity:

  • $R = \rho \frac{L}{A}$ where:

  • $\rho$: Resistivity

  • $L$: Length of the resistor

  • $A$: Cross-sectional area

• The relationship between resistivity at different temperatures:

  • $\rho(T) = \rho_0 (1 + \alpha \Delta T)$

  • Where:

    • $\rho<em>0$ = resistivity at a reference temperature $T</em>0$.

    • $\alpha$ = temperature coefficient of resistivity.

  • $\Delta T = T - T_0$

Example Calculation of Resistance

1. Example from textbook on resistance change with temperature:

   • Given initial temperature: $T<em>0 = 20^{\circ}C$, new temperature: $T = 28^{\circ}C$, $(R</em>0 = 200 \Omega)$.

   • Calculation would give:
     $R = R_0(1 + \alpha \Delta T) = 200(1 + \alpha (28 - 20))$.

   • Result derived was approx. $4.8 \Omega$.

AC and DC Current

• Definition of Types of Current:

  • DC (Direct Current): Current flows in one direction.

  • AC (Alternating Current): Current changes direction, often represented by an oscillating function.

• Graphical representation of current:

  • Variables defined:

  • $x(t)$: Displacement as a function of time.

  • Amplitude is the maximum displacement.

  • Period is the time for a full oscillation.

• Relevant equations involving sine and cosine functions to describe AC behavior:

  • $x(t) = A \sin(2\pi f t)$ for the sine function,

  • $A$ is the amplitude, $f$ is the frequency.

• Key characteristics of current and voltage in AC:

  • Both current (I) and voltage (V) oscillate with respect to time, typically in a synchronized pattern.

Circuit Symbols and Components

• Battery symbol represented with two parallel lines.

• AC source denoted with a circle and a sine wave within it.

• Frequency in home AC supply is typically 60 Hz, indicating the rate of oscillation per second.