# Physics

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- Created by: autopianjew
- Created on: 26-06-17 14:32

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?

Add together

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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

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