Physics 1

Cards (81)

  • Energy is not something you can hold in your hand, it's just an idea
  • Total energy in any interaction is always conserved, energy cannot be created or destroyed
  • Energy can be turned into matter (Mass) but it's still technically true that energy cannot be created or destroyed
  • Energy stores

    Different types of energy
  • Kinetic energy
    Calculated using e = 1/2 mv^2
  • Gravitational potential energy (GPE)

    Calculated using e = mgh
  • Elastic potential energy
    Calculated using e = 1/2 ke^2
  • Thermal energy
    Calculated using e = mc∆T
  • Chemical potential energy is found in food and fuels, there is no equation for it
  • In a closed system, no energy is lost to the surroundings and no energy comes in from the surroundings
  • Gravitational potential energy at the top of a roller coaster
    Converted to kinetic energy at the bottom
  • Rearranging equations to find unknown variables
    1. Divide both sides by mass to get v = sqrt(2gH)
    2. Divide both sides by charge to get V = E/Q
  • If more energy is transferred to the surroundings than the measured temperature change, the calculated specific heat capacity will be higher than the true value
  • Power
    The rate of energy transfer, calculated using P = E/t
  • Efficiency
    Ratio of useful energy output to total energy input, calculated as useful output / total input
  • Electric current
    The flow of electric charge, measured in amps (A)
  • Potential difference (voltage)

    The energy transferred per unit of charge, measured in volts (V)
  • Resistance
    The opposition to the flow of electric current, measured in ohms (Ω)
  • Ohm's law
    1. V = IR
    2. R = V/I
    3. I = V/R
  • Resistance of a resistor is constant (ohmic), but resistance of a bulb changes (non-ohmic)
  • PD and current or V and I
    Directly proportional
  • Graph of PD and current
    • Straight line
    • Negative values for both but still a straight line through the origin
    • Constant gradient shows a resistor has constant resistance
  • Resistance
    Ohm's law: V = I * R (PD in volts = current in amps * resistance in ohms)
  • Steeper gradient of the line
    Lower the resistance of the resistor
  • Graph of PD and current for a bulb
    • Curved graph
    • Resistance is changing
  • Resistance of metal
    Increases with higher PD and higher current
  • Resistors are specially made from specific material such that their resistance stays constant even if the temperature changes
  • Diode
    • Only lets current flow through in one direction
    • In one direction the resistance is very high, in the other it is very low
  • LED (light emitting diode)

    Acts in the same way as a diode but emits light as well
  • Measuring resistance of a metal wire
    1. Connect wire to circuit with crocodile clips
    2. Measure V and I
    3. Calculate R using Ohm's law
    4. Move one clip further up the wire to see how length affects resistance
  • Series circuit
    • Total PD is shared between components
    • Current is the same for all components
    • Total resistance is the sum of all resistances
  • Parallel circuit
    • PD is the same for every branch
    • Current is shared between each branch
    • Total resistance decreases as more resistors are added in parallel
  • Thermistor
    Resistance decreases as temperature increases
  • LDR (light dependent resistor)
    Resistance decreases as light intensity increases
  • Power
    P = VI or P = I^2R
  • Direct current (DC)

    Current that only flows in one direction
  • Alternating current (AC)

    Current that alternates direction, resulting from an alternating PD
  • In a plug, the fuse is attached to the live wire and designed to melt or blow if the current exceeds a certain number of amps
  • Calculating fuse size for an appliance
    1. Use P = VI to find the current
    2. Choose next fuse size up from the calculated current
  • National grid
    • Network of power stations, cables and transformers that transmit electricity across the country