Physics Notes: Thermal, Nuclear, and Electrical Physics

Physics: Thermal, Nuclear, and Electrical Physics

Heating Processes

• Understanding heating, nuclear reactions, and electricity is key to meeting global energy demands.

• Heating, radioactivity (nuclear model of the atom), and nuclear reactions (mass to energy conversion) are explored.

• Analysis and design of electrical systems by investigating the flow of electrical charge in circuits.

What is Physics?

• Deals with energy and matter and their interactions.

• Covers heat, radiation, electricity, motion, sound, light, magnetism, and gravity, explaining energy transfer and transformation.

• Ranges from sub-atomic particles to the universe's edge.

Physics Toolkit: Learning Intentions

• Review scientific notation and SI units.

• Introduce significant figures.

• Use scientific language and symbols.

Success Criteria

• Apply significant figures, scientific notation, and SI units when analyzing data.

• Define validity and reliability.

• Discuss different types of errors.

• Apply correct SI units and convert measurements.

Scientific Notation

• Expresses large or small values easily.

• Numbers in exponential form with one numeral before the decimal point.

• Negative exponents indicate numbers less than 1.

Scientific Notation Examples

• Example:

  • Speed of particle: two hundred million meters per second $= 2.0 \times 10^{8} m/s$

  • Diameter of red blood cell: 2 millionths of a meter $= 2.0 \times 10^{-6} m$

• Specific heat capacity of water: 4,180 J kg-1K-1 $= 4.180 \times 10^{3} J kg^{-1}K^{-1}$

SI Units

• International System of Units

• Examples:

  • Length: meter (m)

  • Mass: kilogram (kg)

  • Time: second (s)

  • Electric current: ampere (A)

  • Temperature: kelvin (K)

  • Amount of substance: mole (mol)

  • Luminous intensity: candela (cd)

Derived Units

• New quantities made of base units

• Examples:

  • Acceleration: metre per second squared $\text{ms}^{-2}$

  • Angle: radian (rad)

  • Area: metre squared $\text{m}^{2}$

  • Density: kilogram per metre cubed $\text{kg m}^{-3}$

  • Electric charge: coulomb (C)

  • Energy: joule (J)

  • Force: newton (N)

  • Frequency: hertz (Hz)

Prefixes

• femto (f): $10^{-15}$

• pico (p): $10^{-12}$

• nano (n): $10^{-9}$

• micro ($\mu$):$10^{-6}$</p></li><li><p>milli (m):$10^{-3}$</p></li><li><p>centi (c):$10^{-2}$</p></li><li><p>deci (d):$10^{-1}$</p></li><li><p>kilo (k):$10^{3}$</p></li><li><p>mega (M):$10^{6}$</p></li><li><p>giga (G):$10^{9}$</p></li><li><p>tera (T):$10^{12}

Volume Conversion Example

• Convert length 35 cm, width 2.0 cm, height 1.5 cm to cubic meters.

Significant Figures

• Indicate uncertainty in measurements.

• Measurements include: best estimate, uncertainty, and unit symbol.

• Report one digit more than known with certainty.

Rules for Significant Figures

1. Non-zero figures are significant.

2. Zeros between non-zeros are significant.

3. Zeros to the right of a non-zero figure but to the left of the decimal point are not significant unless specified.

4. Zeros to the right of a decimal point but to the left of a non-zero figure are not significant.

5. Zeros to the right of the decimal point and following a non-zero figure are significant.

Calculations with Significant Figures

• Multiplying and dividing: use the least number of significant figures.

• Addition and subtraction: round to the least significant decimal place value.

Physics Toolkit: Processing & Analyzing data: Learning Intentions

• Understand the difference between validity & reliability, uncertainty & errors.

• Find the uncertainty of instruments when taking measurements.

Physics Toolkit: Processing & Analyzing data: Success Criteria

• Define terms validity and reliability and discuss different types of errors.

• Determine uncertainty in calculations and measurements.

Precision and Accuracy

• Precision (Reliability): Consistency of a measure.

• Accuracy (Validity): Difference between measured and true value.

Errors

• Random wandering in the data.

• Types of errors:

  • Systematic errors

  • Random errors

• Mistakes are not considered errors.

Systematic Errors

• Cause readings to deviate from the accepted value by a consistent amount in the same direction.

• Affected by the accuracy of the measurement process.

• Types:

  • Zero error

  • Parallax error

  • Calibration error

Systematic errors in graphs

• Often identified when data is graphed.

• If the line of best fit does not go through the origin (0,0) when expected.

• A low systematic error makes the results of an experiment accurate and, therefore, valid.

Random Errors

• Limitations of the measurement equipment and uncontrollable effects on a measurement result.

  • Scale reading limitations: The inability of an instrument to resolve small measurement differences.

  • Solution: take multiple measurements and make an average.

• Results with a low random error (low uncertainty) are said to be precise and reliable.

• On a graph, data points would be scattered on both sides of a trendline.

• An R2 value for a graph tells us about the random error in a graph.

• An R2 value of between 0.98 to 1 is the best fit.

Reporting Repeated Measurements

• Repeated measurements are averaged (mean) to obtain the best estimate of your measurements.

• The mean is found by: mean = \frac{\text{sum of measurements}}{\text{number of measurements}}$</p></li></ul><h4 collapsed="false" seolevelmigrated="true">Uncertainty</h4><ul><li><p>Scales are commonly used in instruments.</p></li><li><p>Printed scales and digital scales come with a degree of uncertainty</p></li><li><p>When reading printed scales, we use a value called ‘half-scale’ division. Eg for 1°C thermometer, the uncertainty is ±0.5°C</p></li><li><p>When recording measurements, you need:</p><ul><li><p>The best estimate- from the instrument</p></li><li><p>Uncertainty (instrument) ± half-scale’ division</p></li><li><p>units</p></li></ul></li></ul><h4 collapsed="false" seolevelmigrated="true">Absolute Uncertainty</h4><ul><li><p>Is the spread of values around the mean reported by half the range of measurements</p></li><li><p>$Absolute Uncertainty = \frac{X{max} - X{min}}{2}$</p></li></ul><h4 collapsed="false" seolevelmigrated="true">Reporting Uncertainty Example</h4><ul><li><p>If the mean has an uncertainty which starts with 1, ie 0.167m, you would round this to two sig figs and round the mean to the same number of decimal places (2dp)</p></li><li><p>Example: If mean is 9.234m/s with an uncertainty of 0.167m/s, then your uncertainty would be rounded to 0.17 and the mean will be rounded to 9.23m/s. Hence the measurement is 9.23±0.17m</p></li></ul><h4 collapsed="false" seolevelmigrated="true">Percentage Uncertainty</h4><ul><li><p>Is is calculated by dividing the absolute uncertainty by the observed measurement and multiplying the result by 100 to give a percentage.</p></li><li><p>$ \text{Percentage Uncertainty} = \frac{\text{Absolute Uncertainty}}{\text{Observed Measurement}} \times 100 $</p></li></ul><h4 collapsed="false" seolevelmigrated="true">Absolute Error</h4><ul><li><p>The difference between the observed (measured X0) value and the accepted value (XA).</p></li><li><p>$ EA = |X0 - XA| $</p></li></ul><h4 collapsed="false" seolevelmigrated="true">Percentage Error</h4><ul><li><p>Absolute error expressed as a percentage</p></li><li><p>$E\% = \frac{|X0 - XA|}{X_A} \times 100$$

Heating and Cooling: Learning Intentions

• Understand the difference between heat, energy and temperature

Heating and Cooling: Success Criteria

• Define heat, energy, temperature and thermal equilibrium.

• Contrast heat, energy and temperature.

Heat and Energy

• Heat is energy transferred due to temperature difference (“energy in transit”).

• Bodies have thermal energy (heat energy).

Temperature: