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M3 > 3.8 Power > Flashcards

3.8 Power Flashcards

1
Q
A
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2
Q

Define energy in the context of physics.

A

Energy is the capacity to do work or transfer heat.

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3
Q

What are the two main types of energy?

A
  • Kinetic energy
  • Potential energy
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4
Q

What is kinetic energy?

A

The energy stored in a moving body, transferred during its acceleration.

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5
Q

What is potential energy?

A

The energy stored by a system which may later be transferred to another energy store.

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6
Q

List examples of potential energy stores.

A
  • Gravitational potential energy
  • Elastic potential energy
  • Electrical potential energy
  • Chemical potential energy
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7
Q

What is the definition of work in mechanical systems?

A

A measure of the energy transferred when a force is applied over a distance.

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8
Q

How is work done measured?

A

In joules (J).

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9
Q

What is one joule equivalent to in terms of force and distance?

A

One joule is the work done when a force of one newton moves a mass over one metre.

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10
Q

In electrical systems, how is work defined?

A

The energy transferred when an electric charge is moved between two points in a circuit.

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11
Q

What unit is used to measure potential difference?

A

Volts (V).

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12
Q

Fill in the blank: Power is the rate at which _______ is done or heat is transferred.

A

work

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13
Q

What is the unit of power?

A

Watts (W) or joules per second (J/s).

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14
Q

How is electrical power defined?

A

The number of joules of energy transferred to or from a circuit in one second.

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15
Q

What is the difference between direct and indirect measurement of electrical power?

A
  • Direct measurement: Using a wattmeter
  • Indirect measurement: Using a voltmeter and an ammeter
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16
Q

What is the function of a voltmeter?

A

To measure potential difference across components in parallel.

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17
Q

What is the function of an ammeter?

A

To measure current in series.

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18
Q

True or False: Power remains constant over time for AC devices.

A

False

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19
Q

What does potential difference measure?

A

The electrical potential energy available per coulomb of charge.

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20
Q

What happens when a current flows through a resistor?

A

Energy is transferred from the electric circuit to the thermal energy store of the resistor

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21
Q

What is the work done by the electric circuit in relation to a resistor?

A

Transferring energy to the resistor and increasing the resistor’s temperature

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22
Q

How does heat flow from a resistor to the surroundings?

A

Through conduction, convection, and radiation

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23
Q

What happens to the heat generated by all components in a circuit?

A

It is dissipated into the air around the components

24
Q

What is the rate at which heat is dissipated called?

A

Power, measured in watts (W)

25
Q

True or False: Resistors are designed to dissipate power.

A

True

26
Q

What limits the maximum power that a particular resistor can dissipate?

A

The resistor’s design and specifications

27
Q

What can happen if the power dissipated exceeds the resistor’s limit?

A
  • The value of the resistor may rise beyond its stated tolerance
  • The resistor may melt (burn out and fuse)
  • The resistor may start a fire
28
Q

Why is it important to observe the correct power rating when designing circuits?

A

To ensure the circuit functions correctly and to prevent hazards

29
Q

Fill in the blank: The heat generated by a resistor flows to the surroundings through _______.

A

conduction, convection, and radiation

30
Q

What is electric power?

A

The rate at which work is done or energy is transformed into an electrical circuit

31
Q

What is the formula for electric power?

A

P = VI

32
Q

In the formula P = VI, what does P represent?

A

Power in watts (W)

33
Q

In the formula P = VI, what does V represent?

A

Potential difference in volts (V)

34
Q

In the formula P = VI, what does I represent?

A

Electric current in amperes (A)

35
Q

What is the power consumption when the current is 1 ampere and the voltage is 1 volt?

A

1 watt

36
Q

If a hydraulic pump has a voltage of 230 V and a current of 4 A, what is its power consumption?

A

920 W

37
Q

Fill in the blank: Power is the product of _______ and _______.

A

voltage, current

38
Q

True or False: The unit of power is measured in watts.

A

True

39
Q

What is the relationship between voltage, current, and power?

A

Power is calculated by multiplying voltage and current

40
Q

What is electrical power (P)?

A

The rate at which work is done or the rate of conversion of energy by an electrical system.

Power can also be expressed in terms of voltage and current.

41
Q

What is the formula for power?

A

Power = work done (joules) / time taken (seconds).

This relationship shows how power relates to work and time.

42
Q

What is the SI unit of power?

A

Watt (W), which is defined as 1 joule per second.

The watt is a measure of electrical power.

43
Q

How can electrical power be expressed using voltage and current?

A

P = V x I

This expression is derived from Ohm’s Law where V = IR.

44
Q

What happens to power if voltage is halved?

A

Only a quarter of the power is obtained.

This is due to the relationship P ∝ V².

45
Q

What happens to power if voltage is doubled?

A

The power is four times larger.

This follows the same principle of P ∝ V².

46
Q

How can power be calculated if resistance is known?

A

P = I²R or P = V²/R

These formulas allow calculation of power without direct current measurement.

47
Q

What is electrical work?

A

Work done when a charge is moved between two points at different electrical potentials.

The formula for electrical work is W = Q x V.

48
Q

What is the SI unit of work?

A

Joule (J).

One joule of work is done when one coulomb moves through a potential difference of one volt.

49
Q

What is the formula for electrical work?

A

Electrical Work (joule) = Charge (coulomb) x Potential Difference (volt).

This shows the relationship between charge and electrical potential.

50
Q

What is electrical energy?

A

The ability of an electrical system to do work.

Energy used is equal to the work done, with both measured in joules.

51
Q

What does the Law of Conservation of Energy state?

A

Energy can neither be created nor destroyed but can be changed from one form to another.

This law emphasizes the transformation of energy rather than its disappearance.

52
Q

What is the multiplier for the prefix ‘mega’?

A

1 000 000 (10^6).

Mega is commonly used in measuring large quantities.

53
Q

How do you convert from low to high exponents in unit conversion?

A

Shift the decimal point to the left.

This method is essential for accurate unit conversions.

54
Q

How do you convert from high to low exponents in unit conversion?

A

Shift the decimal point to the right.

This is the opposite action of converting from low to high exponents.

55
Q

Fill in the blank: The energy a body contains may be determined by calculating the ______ done on the body.

A

work

This reflects the relationship between energy and work done.

56
Q

What is the result of converting 125 microamperes to amperes?

A

0.000125 ampere.

This conversion illustrates the process of shifting the decimal point.

57
Q

What is the result of converting 1 kW to watts?

A

1 000 W.

This demonstrates the conversion from kilowatts to watts by shifting the decimal point.

M3 (19 decks)

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