PHEP 14

Question 1

The resistance of a conductor depends on the nature of?

Answer 1

-the material of the conductor -It’s length - It’s cross-sectional area -It’s temperature

Question 2

The potential difference or voltage drop across any electrical device is the _________ in electrical pressure across the device.

Answer 2

drop

Question 3

What is an electric circuit?

Answer 3

Any path over which current flows

Question 4

A motor converts electrical enery to __________ energy

Answer 4

Mechanical

Question 5

A battery changes electrical energy to _________ energy

Answer 5

Chemical

Question 6

Resistance in a circuit converts electrical energy into?

Answer 6

Heat energy

Question 7

What is the only limiting factor regarding the capacity of electric equipment

Answer 7

The amount of heat energy

Question 8

Electrical power is measured in?

Answer 8

Watts

Question 9

The equivalent resistance of two resistances in parallel equals?

Answer 9

their product divided by their sum (reciprocal method) 1 over 1/R + 1/R

Question 10

A thousand milliwatts is?

Answer 10

1 Watt

Question 11

The resistance of any conductor varies directly as its ____________ and inversely as its ____________

Answer 11

Length; cross-sectinal area

Question 12

Doubling the length of a conductor ____________ its resistance and doubling the cross-sectional area of a conductor __________ its resistance by ___________.

Answer 12

Doubles; reduces; one-half

Question 13

What is the equation for voltage?

Answer 13

E=IR

Question 14

Series circuit - 3 rules

Answer 14

1. I(amps) remains constant 2. E(volts) is additive 3. R (Ohms) is additive

Question 15

Parallel Circuit - 3 rules

Answer 15

1. I(amps) is additive 2. E(volts) remains constant 3. R(Ohms) Rt=(R1xR2)/(R1+R2) or 1/(1/R1+1/R2+1/R3)

Question 16

What is the equation for Power?

Answer 16

P=EI

Question 17

How many watts equals 1 HP

Answer 17

746 watts or 550 ft lbs/sec of work

Question 18

A 5hp motor is supplied from a 240V DC source. There are 100W heat loss in the motor at full load & 320W heat loss in the line supplying the motor. What is the power output of the source in Kilowatts and voltage across the motor terminals? A) 3730kw & 221.5 volts B) 4.15kw & 240 volts C) 4.15kw & 221.5 volts D) none of these answers

Answer 18

C) 4.15kw & 221.5 volts * 1hp = 746 watts its a series circuit=I is constant motor=5hpx746watts = 3,730 watts 3,750w (motor)+320w (line loss)+100w (motor loss) = 4,150w=4.15kw Line drop = Line heat loss / (Total Power / Volts) Ldrop=320 / (4150w/240v) Ldrop=320/17.2916 Ldrop=18.51v Voltage across terminals=Voltage - Line drop Vterm=V-Ldrop Vterm=240v - 18.51v = 221.5v

Question 19

A 240V DC motor draws a current of 37.3 amps. It is used for 8 hours to run a pump. All of the below statements concerning this motor are true except? A) the resistance across the motor terminal will be greater the 10 ohms B) the power output of this motor is 8,952w (true) C) the power output is equivilant to 12hp (true) D) the electrical work done in the 8th hour period is 71.6kw hrs (true)

Answer 19

A) The resistance across the motor terminal will be greater than 10 ohms

Question 20

The reciprocal of the sum of 3 1/5 + 3/5 + 1/3 + 27/15 is

Answer 20

15/89

Question 21

When the direction of current flow is mentioned, the movement of electrons or flow of current means?

Answer 21

The flow from a negative point towards a positive point

Question 22

Equation for electrical energy in watt hours?

Answer 22

W x T (watts multiplied by Time in hours)

Question 23

A length of wire used in a circuit has a resistance of 10 ohms, if the wire is replaced by another wire of the same material but double the length and cross sectional area the resistance would be?

Answer 23

B) 10 ohms *doubling cross-sectional area reduces resistance by 1/2 *doubling the length doubles the resistance 10 ohms/2=5ohms x 2=10 ohms