# Physics

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Define the term: Effeciency
Energy efficiency is a measure of how well a device transfers energy into the form we want.
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What is the calculation for effeciency?
efficiency = ( useful energy transferred ÷ energy supplied ) × 100
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Can effeciency ever be 100 of a product, and why?
No as some of it is always lost to watched energy (heat, sound).
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How can efficiency in mechanical systems be increased?
Making it more aero-dynamic; less heat loss; more lubricated, reduce friction
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What is a U Value?
How much thermal energy transfers each second
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What does a High U-Value show?
More energy transfer every second meaning it loses heat quicker.
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What do resistors in Series circuits do to form a greater resistance?
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What do resistors in a Paralel circuit do to reduce total resistance?
Combine together
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What is the Specific heat capacity of a material mean?
The amount of energy required to raise 1KG of the material by 1C.
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Equation for Energy and their units?
Energy (J) = Mass (KG) * SHC (J/KHc) * Change in temp (C)
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What do large U-Values allow?
They allow heat energy to flow more quickly.
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What effect would reducing the U-Value of a insulator have?
Makes it more efficient at maintaining a temperature and cheaper to insulate/run
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What is the equation for Resistance?
V = I*\$
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In resistance, what does V stand for? And it's unit?
Potential Difference (V)
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In resistance, what does I stand for? And it's unit?
Current (A)
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In resistance, what does R stand for? And it's unit?
Resistance (Ohms)
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The current in a series circuit is what through each component?
The same
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The current in a parallel circuit is the sum of the current in ?
In the seperate branches
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How is the P.D in a series circuit spread?
It's shared
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What is the P.D in a paralel circuit like in each branch of the circuit?
The same
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Unit for Charge?
In Coulombs, C
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Charge (Q) = ?
Charge (Q) = Current (I) (in Amps) * Time (t) (in Seconds)
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In parallel circuits the current is ____ through every component
The same
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In series circuits the voltage across each components does what to the battery voltage?
Adds up to the battery voltage
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What does the voltage of each component in a series circuit depend on?
Depends on it's resistance
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What will never change in a series circuit?
Amps
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If a objects velocity changes, what also will change?
It's momentum.
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Is acceleration a Vector or scalar?
Vector
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What is Scalar?
Only magnitude
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What is Vector?
Both direction and magnitude (size)
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What does displacement mean?
Distance from orginal start point
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No resultant force = ?
No change in momentum
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What does the acceleration of a object depend on? (2 things)
The resultant force applies and the mass of the object
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What is Enertia?
Something which has a resistance to motion
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Momentum is ____
Converved
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An increase in stopping distance is also a increase of?
Impact time + Time of collision
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What is Impact force equal to?
The rate of change of momentum
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Increasing the time of an impact will do what?
Reduce the impact forces (meaning it lasts longer)
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What happens when temperature increases on a resistor of a conductor?
Resistance increases of the conductor
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In low temperature's, the resistance of a thermistor is high meaning?
Little current can flow through
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At high temperatures, the resistance of a thermistor is low, how does this effect current?
More current can flow through
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In the dark; what is the resistance of a LDR like? And what does this mean?
High so little current can flow through
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In the bright light, what is the resistance of a LDR like? And what does this mean?
The resistance of LDR is low, and more current can flow through it.
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## Other cards in this set

### Card 2

#### Front

What is the calculation for effeciency?

#### Back

efficiency = ( useful energy transferred ÷ energy supplied ) × 100

### Card 3

#### Front

Can effeciency ever be 100 of a product, and why?

#### Back ### Card 4

#### Front

How can efficiency in mechanical systems be increased?

#### Back ### Card 5

#### Front

What is a U Value?

#### Back 