Flashcards in Chapter 26 Deck (27):

1

## What is Direct Current?

###
In Direct (DC) Current, the emf and currents are constant

eg) circuits involving batteries

2

## What is Alternative Current?

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In Alternative (AC) Current, the emf and current oscillate in time

eg) circuits involving a generator

3

## What is AC Voltage?

###
The output of an AC Generator is sinusoidal and oscillates in time according to...

E = Eocos(2πft) = Eocos(2πt/T)

E - the instantaneous voltage at a given time

Eo = the maximum (or peak) voltage

T = is the period (the time for one full cycle)

f = 1/T = w/2π is the frequency (# of cycles/ time)

4

## What are Resistors in AC circuits?

###
Kirchhoff's rules and Ohm's Law still hold in AC Circuits in AC Circuits:

v(R) = V(R)cos(2πft)

i(R) = v(R)/R = V(R)cos(2πft)/R = I(R) = cos(2πft)

5

## What is the average Power dissipated by AC Circuits?

### P(R) = (1/2)I^2R

6

## What is Root Mean Square (RMS) Voltage and Current?

### Irms = I(R)/√2 Vrms = V(R)/√2

7

## What are Transformers?

### An AC transformer consists of two coils of wire wound a core of soft iron

8

## What is the Primary (N1) or (Np)?

### the side connected to the input AC voltage source is called the PRIMARY and has N1 turns

9

## What is the Secondary (N2) or (Ns)?

### The other side, is called the secondary, is connected to a resistor and has N2 turns

10

## What is the load?

### The secondary is connect to a resistor called the load

11

## What is a Step-Up transformer?

### When N2>N1 the transformer is referred to as a Step-Up Transformer: it raises the voltage

12

## When is a Step-Down transformer?

### When N2

13

## What are the formulas for a Step-Up and a Step-Down transformer?

###
V2=(N2/N1)*V1 V2(rms)=(N2/N1)*V1

I2=(N1/N2)*I1 I2(rms)=(N1/N2)*I1(rms)

14

## What does is a Grounder?

### Earth is a conductor, a circuit connected, to the earth is considered grounded

15

## What is an Electrical Outlet?

### Outlets are connected in parallel. Electricity provided by the power company is transmitted to outlets through wires in the walls

16

## What is the neutral side of an electrical Outlet?

### one terminal of the electricity supply is grounded, this is called the Neutral side

17

## What is the Hot side of an Electrical Outlet?

### the other side has varying potential, each outlet has two slots, one connected to each side

18

## What is a Breaker?

### A circuit breaker limits the current in each circuit. If an ammeter measures too much current, it sends a signal to open the switch to disconnect the circuit

19

## What is a Ground Fault Interrupter?

###
outlets (GFI) have built in sensing circuit that compares the currents int he hot and neutral wires

- The current in these wires should be the same

20

## What is an Induced Electric Field?

### This means that there is an electric field, and induced electric field, pointing in the direction of the current

21

## What induces and Electric Field?

###
a changing magnetic field induces, the an electric field, independently of any charges

- The induced electrical field produces a current, which produces a magnetic field

22

## What are Electromagnetic Waves?

###
Electric and Magnetic fields play symmetric roles in nature

- If E and B change in just the right way there is a self-sustaining electromagnetic field

23

## What induces a Magnetic field?

### a changing electric field induces a magnetic field, independently of any wires or chargers

24

## When ranking AC/LR circuits based on the current through the battery immediately after the switch is closed. What do you do?

### You make the inducer, an "Open" as if it were an open space in the circuit or and open switch

25

##
When ranking Ac/LR circuits based on the current through the battery a very long time after the switch is closed. What do you do?

### You make the inducer a "Short" imagine replacing the inductor with a bare wire

26

## Inductance is Measured in what?

###
The symbol for Inductance is L

SI Unit is Henry's (H)

27