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Viktor [21]
4 years ago
6

One AA battery in a flashlight stores 9400 J. The three LED flashlight bulbs consume 0.5 W. How many hours will the flashlight l

ast?
Engineering
1 answer:
Effectus [21]4 years ago
7 0

Answer:

time = 5.22 hr

Explanation:

Given data:

Energy of battery = 9400 J

Power consumed by three led bulb is 0.5 watt

we know Power is give as

Power = \frac{ energy}{time}

plugging all value and solve for time

time = \frac{energy}{power}

time = \frac{9400}{0.5}

time = 18,800 sec

in hour

1 hour = 3600 sec

therefore in 18,800 sec

time = \frac{18800}{3600} = 5.22 hr

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Design a half-wave recti er which provides a peak voltage of 15 V, and anaverage voltage of 3.8 V when driven by a 120 V (rms) a
nirvana33 [79]

Answer:

You need a 120V to 24V commercial transformer  (transformer 1:5), a 100 ohms resistance, a 1.5 K ohms resistance and a diode with a minimum forward current of 20 mA (could be 1N4148)

Step by step design:

  1. Because you have a 120V AC voltage supply you need an efficient way to reduce that voltage as much as possible before passing to the rectifier, for that I recommend a standard 120V to 24V transformer.  120 Vrms = 85 V and 24 Vrms = 17V = Vin
  2. Because 17V is not 15V you still need a voltage divider to step down that voltage, for that we use R1 = 100Ω and R2 = 1.3KΩ. You need to remember that more than 1 V is going to be in the diode, so for our calculation we need to consider it. Vf = (V*R2)/(R1+R2), V = Vin - 1 = 17-1 = 16V and Vf = 15, Choosing a fix resistance R1 = 100Ω and solving the equation we find R2 = 1.5KΩ
  3. Finally to select the diode you need to calculate two times the maximum current and that would be the forward current (If) of your diode. Imax = Vf/R2 = 10mA and If = 2*Imax = 20mA

Our circuit meet the average voltage (Va) specification:

Va = (15)/(pi) = 4.77V considering the diode voltage or 3.77V without considering it

6 0
4 years ago
In a much smaller model of the Gizmo apparatus, a 5 kg mass drops 86 mm (0.086 m) and raises the temperature of 1 gram of water
Orlov [11]

Answer:

The amount of energy transferred to the water is 4.214 J

Explanation:

The given parameters are;

The mass of the object that drops = 5 kg

The height from which it drops = 86 mm (0.086 m)

The potential energy P.E. is given by the following formula

P.E = m·g·h

Where;

m = The mass of the object = 5 kg

g = The acceleration de to gravity = 9.8 m/s²

h = The height from which the object is dropped = 0.086 m

Therefore;

P.E. = 5 kg × 9.8 m/s² × 0.086 m = 4.214 J

Given that the potential energy is converted into heat energy, that raises the 1 g of water by 1°C, we have;

The amount of energy transferred to the water = The potential energy, P.E. = 4.214 J.

6 0
3 years ago
Why might construction crews want to install pipes before the foundation is poured?
denpristay [2]
I’m a concrete mason myself and I can tell you it is a pain in the butt to Roto hammer a hole into the concrete to put the pipe in it’s a lot easier to just pour the concrete around it
6 0
3 years ago
A closed system consists of 0.3 kmol of octane occupying a volume of 5 m³. Determine (a) the weight of the system, in N, and (b)
Leni [432]

Answer:

a) m=336.18N

b) Vn=16.67m/kmol

Vm=0.1459m^3/kg

Explanation:

To calculate the mass of the octane(m):

Number of mole of octane (n) =0.3kmol(given)

Molarmass of octane (M) =114.23kg/kmol

m=n*M

m=(0.3kmol)*(114.23kg/kmol)

m=34.269kg

To calculate for the weight of octane(W):

W=g*m

W=(9.81m/s^2)*(34.269kg)

W=336.18N

b) For specific volumes of Vn and Vm:

Given volume of octane (V) =5m^3

Vm=V/m

Vm=5m^3/34.269kg

Vm=0.1459m^3/kg

And Vn will be :

Vn=V/m=5m^3/0.3kmol

Vn=16.67m/Kmol

Therefore, the answers are:

a) m=336.18N

b) Vn=16.67m/kmol

Vm=0.1459m^3/kg

7 0
3 years ago
Write a GUI-based program that plays a guess-the-number game in which the roles of the computer and the user are the reverse of
AURORKA [14]

Answer:

import javax.swing.*;

import java.awt.*;

import java.util.Random;

import java.awt.event.*;

public class Guess extends JFrame

{

   private static final long serialVersionUID = 1L;

   private JButton newGame;

   private JButton enter;

   private JButton exit;

   private JTextField guess;

   private JLabel initialTextLabel;

   private JLabel enterLabel;

   private JLabel userMessageLabel;

   private int randNum;

   private int userInput;

   private int maxtries = 0;

   public Guess()

   {

       super("Guessing Game");

       newGame = new JButton("New Game");

       exit = new JButton("Exit Game");

       enter = new JButton("Enter");

       guess = new JTextField(4);

       initialTextLabel = new JLabel("I'm thinking of a number between 1 and 100. Guess it!");

       enterLabel = new JLabel("Enter your guess.");

       userMessageLabel = new JLabel("");

       randNum = new Random().nextInt(100) + 1;

       setLayout(new FlowLayout());

       add(initialTextLabel);

       add(enterLabel);

       add(guess);

       add(newGame);

       add(enter);

       add(exit);

       add(userMessageLabel);

   

       setSize(500, 300);

       addWindowListener(new WindowAdapter()

       {

           public void windowClosing(WindowEvent e)

           {

               System.exit(0);

           }

       });

       newGameButtonHandler nghandler = new newGameButtonHandler();

       newGame.addActionListener(nghandler);

       ExitButtonHandler exithandler = new ExitButtonHandler();

       exit.addActionListener(exithandler);

       enterButtonHandler enterhandler = new enterButtonHandler();

       enter.addActionListener(enterhandler);

   }

   class newGameButtonHandler implements ActionListener

   {

       public void actionPerformed(ActionEvent e)

       {

           setBackground(Color.ORANGE);

           guess.setEnabled(true);

           guess.setText("");

           enter.setEnabled(true);

           maxtries = 0;

           userMessageLabel.setText("");

           randNum = new Random().nextInt(100) + 1;

       }

   }

   class ExitButtonHandler implements ActionListener

   {

       public void actionPerformed(ActionEvent e)

       {

           System.exit(0);

       }

   }

   class enterButtonHandler implements ActionListener

   {

       public void actionPerformed(ActionEvent e)

       {

           userInput = Integer.parseInt(guess.getText());

           checkGuess(randNum);

      if(userInput > 100 )

          {

                               userMessageLabel.setText("invalid entry");

          }

       }

   }

   public void checkGuess(int randomNumber)

   {

       maxtries++;

     if(maxtries==10){

           userMessageLabel.setText("You Lose!!");

           guess.setEnabled(false);

           enter.setEnabled(false);

         

       }else if (userInput == randomNumber)

           {

               userMessageLabel.setText("Correct !");

           }

       else if (userInput > randomNumber)

           {

               userMessageLabel.setText("Too high");

           }

       else if (userInput < randomNumber)

           {

               userMessageLabel.setText("Too Low");

           }

   }

   public static void main(String[] args)

   {

       Guess game = new Guess();

       game.setVisible(true);

   }

}

8 0
3 years ago
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