unit 9 - circuits
charge and electric force (coulombs law)
electric charge
electric potential energy and electric potential
circuits
ohm's law
charge and electric force (coulombs law)
electric charge
- An electric charge can be positive or negative
- A neutral object has an equal amount of positive and negative charges
- Elementary charge- Smallest unit of charge that can be isolated = 1.6 * 10^-19 C
- Variable for charge = q
- Units for charge = Coulombs (C)
- Opposite charges attract, like charges repel
- Coulomb's Law- The electric force increases as the charges increase, and electric force decreases as the distance between the particles increases
- The electric force is the absolute value of the charges
- Electrostatic Induction- Ability of charges in one object to affect changes in another
- A charged object can be charged through friction or contact
- Conductors - electrons can move
- Insulators - electrons can't move
- Polarized Objects - net charge is zero (one side negative, one side positive)
electric potential energy and electric potential
- Electric Potential- Amount of energy it would take to bring an elementary charge to a specific location within an electric field
- Voltage- Measurement of the electromotive force (emf) or the difference in electric potential
- High voltage = A particle will lose a lot of electric potential energy while moving (high potential difference)
circuits
- Series circuit - One item after another (current passes through each element)
- Resistors in series - Add up the resistance in each one to find the equivalent resistance
- Parallel circuit - Different circuits connected (multiple paths)
- Resistors in parallel - Add up the reciprocals of all of the resistors and then take the reciprocal of that number
ohm's law
- Resistivity - Property of a material that opposes flow of charge (structure and temp)
- Something that allows flow - Low resistivity
- Doesn't allow flow - High resistivity
- Resistance - Measurement of the difficulty for charges to flow (see equation to the right)
- Current (I) - How many electrons are moving
- Voltage (V) - Potential energy difference
- Resistance (R) - Measurement of the difficulty for charge to flow
- Kirchhoff's Loop Rule - Sum of all voltages is 0 (conservation of energy in a circuit)
- Kirchhoff's Junction Rule - Current entering a junction = current leaving a junction (conservation of charge)
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