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17 Cards in this Set
- Front
- Back
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What happens to resistors when current flows through them?
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They get hot. There is an energy transfer which heats resistor
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What does the heating effect do to the resistor?
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Increases resistance so less current flows through or greater voltage needed to produce same current
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Are fuses resistors?
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Yes, in a way! They resist and heat up if too much current, eventually melting
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Name some appliances that use this resistance effect
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Toaster: has coil that has high resistance. this heats up with current and temp increases so wire glows. Bread toasts with infrared radiation.
Light bulbs too!! |
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What is electrical power?
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The rate at which an appliance transfers energy. If an appliance has a high power rating it transfers lots in short time.
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What influences this consumption?
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The current! Large power rating will draw a large current from supply
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What is power measured in?
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Watts (W)
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What is the formula for electrical power?
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Power = current x voltage
p = i x v |
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What do most electrical goods show?
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Power rating and voltage
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How should fuses be rated?
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As near as possible but higher than normal operating current
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How do you work out what fuse is required?
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Work out the current.
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A hair dryer is rated at 230v with 1kW power rating. What fuse?
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1kW = 1000W
i = p/v so 1000/230 = 4.3A Need 5A fuse |
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What are the most common fuse ratings?
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3, 5 and 13 A
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What happens when electricity flows through a component?
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Energy is transferred. e.g. in a light bulb electrical energy is transferred to light and heat energy
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What does the amount of energy transferred depend on?
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The current, the voltage and how long it is on for
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What is the formula for energy transferred?
What are the units? |
Energy transferred = current x voltage x time
Joules (J) |
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The motor of an elec toothbrush is attached to a 3v battery. if 0.8A flows through motor for 3 mins what is energy transferred
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0.8 x 3 x (3 x 60) = 432 J
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