# DC Principles Flashcards Preview

## Electrical > DC Principles > Flashcards

Flashcards in DC Principles Deck (45)
1
Q

What are the names and units for; Charge Current Voltage

A

Charge (q) - coulomb (C) Current (i) - Ampere (A) Voltage (v) - Volt (V)

2
Q

A current is a….

A

Coulomb per second

3
Q

A volt is a…

A

Joule per coulomb

4
Q

What’s the charge on an electron?

A

-1.6x10^-19C

5
Q

Current(i) = ?

A

i(t)=dq(t)/dt = Charge/Time

6
Q

Total charge through a conductor q(t) = ?

A

q(t) = t(integral)t0 i(t)dt + q(t0)

7
Q

Voltage is…

A

The energy transferred per unit charge that flows through the element

8
Q

A watt is a…

A

Joule per second

9
Q

Power =

A

Voltage x Current

10
Q

If energy is ____ it is positive but if it is supplied it is ____

A

If energy is absorbed it is positive but if it is supplied it is negative

11
Q

Equation to calculate the power delivered to a circuit element between time instants t1 and t2

A

w = t2(intergral)t1 p(t)dt

12
Q

The net current entering and leaving a node is?

A

0

13
Q

State Kirchoff’s Voltage Law

A

The algebraic sum of the voltages equals zero for any closed path (loop) in an electrical circuit

14
Q

In conductors, the voltage between any 2 points of an ____ conductor is ____ regardless of the current

A

In conductors, the voltage between any 2 points of an ideal conductor is zero regardless of the current

15
Q

When 2 points are connected by an ideal conductor they are ____ together

A

Shorted

16
Q

There is an open circuit between two parts of the circuit when?

A

There are no conductors or other circuit elements connected between 2 parts of a circuit

17
Q

Dependant voltage sources (also knows as ____ ____ ____) are represented by?

A

(Controlled voltage sources) Diamond shapes

18
Q

Resistance = ? and ?

A

R=V/I and R=(pL)/A

19
Q

Voltage is ____ to ____ in an ideal resistor

A

Voltage is proportional to current in an ideal resistor

20
Q

Typical values of resistivity for Conductors = conductors = Insulators =

A

Conductors = 10^-8 conductors = 0.1 Insulators = 10^21 (‘infinity’)

21
Q

Conductance is? and so (Symbol, equation and unit)

A

G which is 1/R and so Ohms^-1 and so i=Gv

22
Q

Energy = ? (for a battery)

A

Q.v

23
Q

Q = ?

A

i.T

24
Q

Energy = ? (2 obvious ones)

A

mgh and 1/2mv^2

25
Q

Energy density = ?

A

Energy (J) / Mass (kg)

26
Q

Conductances in series and parallel is…?

A

Opposite to resistance

27
Q

Voltage divider?

A

V1 = R1 x i = R1 / (R1+R2+R3) x Vtotal

28
Q

Fraction of voltage is ratio of…?

A

Given resistance / total resistance

29
Q

Fraction of current is ratio of…?

A

Other resistance / total resistance

30
Q

For current division - i1 = ? and i2 = ?

A

i1 = v/R1 = R2/R1+R2 x itotal and i2 = v/R2 = R1/R1+R2 x itotal

31
Q

The current flowing from node n toward node k is given by…?

A

(Vn-Vk)/Rx

32
Q

Avoid writing ____ equations for loops that include ____ sources

A

Avoid writing KVL equations for loops that include current sources

33
Q

To ‘zero’ a voltage source you…

A

Replace it with an short circuit

34
Q

To ‘zero’ a current source you…

A

Replace it with an open circuit

35
Q

The load resistance that maximises the power delivered to the load from a two-terminal circuit is equal to…?

A

The Thévenin resistance (also called the output resistance) of the circuit

36
Q

Maximum power results in…?

A

Plmax = Vt^2/4Rt

37
Q

iL = ?

A

iL = Vt/(Rt+RL)

38
Q

Electrons with never go through a wire with ____, it will always go the ____ ____

A

Electrons will never go through a wire with resistance, it will always go the other way

39
Q

Anything in parallel with a empty wire makes…?

A

0V

40
Q

The total response is…

A

The sum of the responses to each of the independent sources acting individually

41
Q

A resistance that obeys Ohm’s law is…?

A

Linear

42
Q

What only applies to linear circuits?

A

Superposition

43
Q

What is used to measure unknown resistances?

A

The Wheatstone bridge

44
Q

When is the Wheatstone bridge balanced?

A

when ig = 0 and Vab = 0

45
Q

For the Wheatstone bridge, Rx = ?

A

Rx = (R2/R1)R3