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3 years ago

What is Back EMF? How does it limits the speed of a permanent magnet DC?

Engineering

1 answer:

ss7ja [257]3 years ago

8 0

Answer and Explanation:

The DC motor has coils inside it which produces magnetic field inside the coil and due to thus magnetic field an emf is induced ,this induced emf is known as back emf. The back emf always acts against the applied voltage. It is represented by $E_b$

The back emf of the DC motor is given by $E_b=\frac{NP\Phi }{60A}$

Here N is speed of the motor ,P signifies the number of poles ,Z signifies the the total number of conductor and A is number of parallel paths

As from the relation we can see that back emf and speed ar dependent on each other it means back emf limits the speed of DC motor

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You are preparing to work with Chemical A. You open the appropriate storage cabinet, and notice Chemical B, as well as Chemical

PtichkaEL [24]

The correct answer is; Stability and reactivity.

Further Explanation:

The stability and reactivity section of the SDS sheets is where to check for the possibility of hazardous reactions for the chemicals. This also lists the chemical stability of each chemical that people may be using. This can be found in section 10 of the OSHA Quick Card.

The SDS sheets has 16 sections for employees to use. Since 2015, the sections can be found in uniform format for easier and faster ways to find the section needed. The 16 sections for the SDS sheets are:

Identification
Hazard(s) identification
Composition/information on ingredients
First-aid measures
First-aid measures
First-aid measures
Handling and storage
Exposure controls/personal protection
Physical and chemical properties
Stability and reactivity
Toxicological information
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4 years ago

A sports car has a drag coefficient of 0.29 and a frontal area of 20 ft2, and is travelling at a speed of 120 mi/hour. How much

Andrej [43]

Answer:

Power required to overcome aerodynamic drag is 50.971 KW

Explanation:

For explanation see the picture attached

4 0

3 years ago

Assume we have already defined a variable of type String called password with the following line of code: password' can have any

omeli [17]

Answer:

The Java code is given below with appropriate comments for better understanding

Explanation:

import java.util.Scanner;

public class ValidatePassword {

public static void main(String[] args) {

Scanner input = new Scanner(System.in);

System.out.print("Enter a password: ");

String password = input.nextLine();

int count = chkPswd(password);

if (count >= 3)

System.out.println("Secure");

else

System.out.println("Not Secure");

}

public static int chkPswd(String pwd) {

int count = 0;

if (checkForSpecial(pwd))

count++;

if (checkForUpperCasae(pwd))

count++;

if (checkForLowerCasae(pwd))

count++;

if (checkForDigit(pwd))

count++;

return count;

}

// checks if password has 8 characters

public static boolean checkCharCount(String pwd) {

return pwd.length() >= 7;

}

// checks if password has checkForUpperCasae

public static boolean checkForUpperCasae(String pwd) {

for (int i = 0; i < pwd.length(); i++)

if (Character.isLetter(pwd.charAt(i)) && Character.isUpperCase(pwd.charAt(i)))

return true;

return false;

}

public static boolean checkForLowerCasae(String pwd) {

for (int i = 0; i < pwd.length(); i++)

if (Character.isLetter(pwd.charAt(i)) && Character.isLowerCase(pwd.charAt(i)))

return true;

return false;

}

// checks if password contains digit

public static boolean checkForDigit(String pwd) {

for (int i = 0; i < pwd.length(); i++)

if (Character.isDigit(pwd.charAt(i)))

return true;

return false;

}

// checks if password has special char

public static boolean checkForSpecial(String pwd) {

String spl = "[email protected]#$%^&*(";

for (int i = 0; i < pwd.length(); i++)

if (spl.contains(pwd.charAt(i) + ""))

return true;

return false;

}

5 0

3 years ago

1. A hydro facility operates with an elevation difference of 50 m and a flow rate of 500 m3/s. If the rotational speed is 90 RPM

zloy xaker [14]

Answer:

a) Pelton Turbine

b) $P=2.42*10^{5}KW$

Explanation:

From the question we are told that:

Height $h=50$

Flow Rate $R= 500 m^3/s$

Rotational speed $\omega=\90 RPM$

Let

Density of water

$\rho=1000$

Generally the equation for momentum is mathematically given by

$P=\rho gRh$

$P=1000*9.81*500*50$

$P=2.42*10^{5}KW$

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3 years ago

What minimum radius of curvature may be designed for safe operation of vehicles at 70 mi/hr if the maximum rate of superelevatio

aleksandr82 [10.1K]

Tell me why i got this question got it right and now won’t remember but i’ll get back at you when i remember

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3 years ago