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22 Cards in this Set
- Front
- Back
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Changes in energy stores |
Energy can be stored in a variety of different energy stores energy can be transferred by: heating, waves, electronic current, of by a force when it moves on an object When an object falls and gains speed it’s store of gravatatinal potential energy decreases and kinetic energy stores increases |
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Conversation of energy |
Energy can not be created or stored. Conservation of energy applies to all energy changes Energy cannot be transferred on a closed system. It is the same before and after. |
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Closed system |
A closed system is a isolated system in which no energy transfers take place out of or into the energy stores of the system |
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Gravitational potential energy stores. |
The gravatatinal potential energy store of an object increases when it moves up and decreases when it moves down. The GPE stores of an object increases beciase work is done on it to overcome the gravatatinal force |
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Kinetic energy stores |
The energy in a kinetic energy stores of a moving object depends on its mass and speed Kinetic energy = 1/2 * mass * speed ^2 |
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Elastic energy stores |
Elastic potential energy is the energy stored in an elastic object when work is done on the object Elastic potential energy = 1/2 * spring constant * extension^2 |
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Energy dissipation oowry |
Useful energy is the place we want it and in the form we need it Wasted energy is the energy that is not useful energy and is transferred by an undesired pathway Wasted energy is eventual transferred to the surroundings which become warmer As the energy dissipates (spreads out) it gets less and less useful. |
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Energy and efficiency |
Efficiency = useful output energy / total input energy into devise Energy transferred can not be more than 100% Machines waste energy becuase of the friction between their moving parts, air resistance, electrical resistance , and noise |
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Power |
Power is a rate of transferred energy Power = energy (joules) / time taken (seconds) |
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Potential difference (volts) |
Current (amps) X resistance (ohms) |
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Electrical current and electrical charge |
An electrical current is a flow of eletrical charge. In electric circuits this charge is often carries by ions in an electrolyte. |
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Ohms law |
States that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor Reversing the potential difference across a resistor reverses the current though it. |
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Ohms law |
States that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor Reversing the potential difference across a resistor reverses the current though it. |
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Resistance formula |
Potential difference / current |
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Diode |
Forwards resistance low; reverse resistance High |
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Ohms law |
States that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor Reversing the potential difference across a resistor reverses the current though it. |
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Resistance formula |
Potential difference / current |
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Diode |
Forwards resistance low; reverse resistance High |
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A filaments lamp resistor |
A filaments lamps resistance increases if the filaments temperatures incresses |
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A thermistor resistor |
It’s resistance decreases as it’s temperature decreases |
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A thermistor resistor |
It’s resistance decreases as it’s temperature decreases |
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An LDR resistor |
An LDR resistance decreases if the light intensity on it increases |
