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# Power

### Determining the Radius of a Model Earth From Scale Data

Using different scales, find the radius of earth. Imagine a scale model of the Universe, where a model of Earth is in London and a model of a very distant galaxy is in Venice. In this scale model, the Earth would be represented by a tiny sphere. Use the information below to calculate the radius of the model Earth. Give your a

### Energy Dissipated in a Resistor

A capacitor C is charged from a 10V supply through a resistor, and is then fully discharged again so that its voltage cycles from 0 to 10V and back to 0. Find the energy dissipated in the resistor, the energy stored in the capacitor, and energy drawn from the voltage source in this cycle.

### Calculate the Energy to Melt Ice and Change the Temperature

A glass contains 0.25kg of water at 0c, 0.15kg of ice, also at 0c, is added to water and it is noticed that after 11 minutes all the ice has melted and all the water is now at 15c. Assuming that the thermal capacity of the glass may be ignored, calculate the thermal energy absorbed by the ice for t to melt. total thermal e

### Wind turbine mechanical torque delivered to a generator

Determine wind turbine mechanical torque delivered to the generator or gearbox) Rotor diameter = 100m radius R = 50 m Rotor speed= 13 rpm ? = 13*2?/60 rad/s Swept area = 7854m2 Blades = 48.7m Hub Height= 80m Wind Velocity= 13 m/s Air density= 1.225 kg/m3 CP = 0.27

### True and False Questions about Transformers

A transformer is an electrical device that can change the voltage from one value to another, based on the principle of Faraday's Law of Induction. Consider a transformer with Np turns of wire in the primary (input) circuit and Ns turns in the secondary (output). Which of the following statements are true? Briefly justify your an

### total power emitted by a 25C Microwave Transmitter

A microwave transmitter emits electromagnetic waves of a single wavelength. The maximum electric field 1.27 km from the transmitter is 6.74 V/m. Assuming that the transmitter is a point source, calculate the total power emitted by the transmitter.

### Parallel Circuit with a battery and three identical light bulbs

Q12: Parallel Circuit Consider the circuit shown below, with a battery and three identical light bulbs, and a switch connecting the third bulb to the circuit. Initially, the switch is open. Now, we are going to close the switch. Which of the following statements are true when the switch is closed (compared to the initial state,

### Calculate the rms electric field in the sunlight that hits Saturn

Calculate the rms electric field in the sunlight that hits Saturn, knowing that the Earth receives about 1340 W/m2 and that Saturn is 9.54 times farther away from the Sun (on average) than is the Earth. Please solve and explain problem.

### Power output of machine, horizontal recoil speed of a gun, speed of the bullet

1. Compute the power output of a machine that lifts a 500-kg crate through a height of 20.0 m in a time of 60.0 s. 2. A 1200-kg gun mounted on wheels shoots an 8.00-kg projectile with a muzzle velocity of 600 m/s at an angle of 30.0°; above the horizontal. Find the horizontal recoil speed of the gun. 3. A 2.0-kg block of

### Copper wire length, iron wire resistance, cost of hall light

The answers are give but please provide the solutions. Resistivity Problems: 1. How long should a copper wire 0.4mm in diameter be for it to have a resistance of 10ohms? The resistivity of copper is 1.7 x 10-8 Q-m Answer: 74m 2. An iron wire has a resistance of 0.20ohms at 20°C and a resistance of 0.30ohms at 110°C.

### Calculate total power emitted by a microwave transmitter.

A microwave transmitter emits electromagnetic waves of a single wavelength. The maximum electric field 1.27 km from the transmitter is 6.74 V/m. Assuming that the transmitter is a point source, calculate the total power emitted by the transmitter.

### Electricity Resistance Voltage

1. A wire 1 mm in diameter is connected to one end of a wire of the same material 2 mm in diameter of twice the length. A voltage source is connected to the wires and a current is passed through the wires. If it takes time T for the average conduction electron to traverse the 1-mm wire, how long does it take for such an electro

### Physics: Population Growth and World Energy Use

Show all work step by step and provide justifications and source. Population Growth and World Energy Use a. The entire world would (mostly) like our standard of living, which as you have seen, implies the same energy consumption rate that the US has (300x106 BTU per person per year). If the world consumed energy at the

### Physics: Series and Parallel resistors. Which statements are true?

You have two resistors with different values. They may be combined either in series or in parallel, and that combination is then connected to a battery. Which of the following statements are true? (T/F) to minimize the total power coming out of the battery, the resistors should be connected in parallel. (T/F) to minimize

### Power, Voltage and Current

Household wiring has a 120 V source for nearly all circuits, including your light bulbs. Imagine that you have two separate circuits with two different light bulbs plugged into the wall socket -- a 60 W bulb and a 120 W bulb. Which of the following statements are true about the comparison between these two circuits? 1. the v

### Series circuit, propulsion, resistance, power costs, transformer

1. A series circuit consists of 10,000, 20,000, and 30,000 ohm resistors connected in series across a 10-volt battery. Determine the current in the circuit? 2. Determine the propulsion force between two electric charges of 3 x and 7 x separated by a distance of 2 meters. (k=9,000,000,000 3. Determine the power con

### 7 Physics questions: resistance, power, current, series & parallel circuits, magentic

1. Find the resistance of a light bulb that is connected to a 120-volt line and has a current of 0.5 amps flowing through it. 2. Calculate the electrical power of a lamp that carries 2 amps of current at 120 volts. 3. A heater uses 20 amps when connected to a 100-volt line. If the electric power costs 10 cents per kilowa

### Strength of the Magnetic Field

A 10 cm long wire is pulled along a U-shaped conducting rail in a perpendicular magnetic field. The total resistance of the wire and rail is 0.20 ohms. Pulling the wire with a force of 1.oN causes 4.0 W of power to be dissipated in the circuit. A) What is the speed of the wire when pulled with 1.0N? B) What is the strength of

### Solving for Example Physics Problems

1. Two charges are placed at opposite ends of a meter stick. Approximately where could a third charge be placed so it would be in equilibrium? 2. A 2 C charge and a 8 C charge repel each other with 10 N of force. How much will a 4 C charge and a 4 C charge repel each other when placed the same distance apart? A. 40 N B. 20 N

### Electricity: Power dissipated by a resistor

The voltage drop across an electrical resistor is 10 volts and the current through it is 1 ampere. The total heat capacity of the resistor is 20 J/K, and heat dissipated from the resistor to the surrounding air according to the relation: Q = -h(T-Tam) Where Tam is the ambient air temperature, 25 deg.C; T is the temperature o

### Solving Problems Involving Work, Energy & Power

Please help with the following problem. A Bungee Jumper jumps off of height H and just reaches the bottom of the cliff with a zero velocity. Just before her cable snaps her back upward, while she is motionless, she grabs a rock of mass m1. You observe that the jumper achieves the height h on the way back up. What is m1?

### Loudspeakers power output.

At a recent rock concert, a dB meter registered 128 dB when placed 1.60 m in front of a loudspeaker on the stage. (a) What was the power output of the speaker, assuming a hemispherical radiation of the sound and neglecting absorption in the air? ___________ W (b) How far away would the intensity level be a somewhat reasonable

### Intensity and power as functions of distance

The intensity of a particular earthquake wave is measured to be 3.0 E6 J/m2·s at a distance of 45 km from the source. (a) What was the intensity when it passed a point only 3.0 km from the source? 1 J/m2·s (b) What was the rate energy passed through an area of 15.0 m2 at 3.0 km?

### Torque, Power and Friction

An electric motor can accelerate a Ferris wheel of moment of inertia I = 22000 kgm^2 from rest to 11.0 rev/min in 12.0 s. When the motor is turned off, friction causes the wheel to slow down from 11.0 to 9.0 rev/min in 10.0 s. Determine the torque generated by the motor to bring the wheel to 11.0 rev/min______Nm Determine t

### AC Transformer Number of Turns and Maximum Power

A transformer for an answering machine takes an AC voltage of 170V (maximum, or peak-to-peak) as its input and provides 7.8V (rms) as its output to the answering machine. A) What is the turns ratio between the primary and secondary? B) When not answering, the machine uses a maximum power of 5.0W. What is the current (rms) dr

### Alternating Currents: LRC circuits, resonance

An L-R-C series circuit is connected to an AC source of constant voltage amplitude V and variable angular frequency w. A) Show that the current amplitude, as a function of w See Eq 1 B) Show the average power dissipated in the resistor See Eq 2 C) Show that I and P are both maximum when the source frequency equals

### Transformer Features for Voltage Ratio

A transformer used in a computer steps down the 120 V from the wall outlet to 5 V. The computer uses 6 A of current to operate the ICs and various components like disk drives and memory. (a) What turns ratio NP/NS is required to achieve the voltage ratio? (b) How much power does the computer use? (c) If the

### Nine multiple choice questions on mechanics (force, work, energy, power, moment, torque)

1. An offensive lineman weighs twice what you weigh, and has three times your arm strength. You are trying to push him out of the way. The magnitude of the force he exerts on you will be: A. six times the force you exert on him. B. three times the force you exert on him. C. twice the force you exert on him. D. the same as t

### To determine focal length of eyepiece of a microscope.

A standardized biological microscope has an 8.0mm focal-length objective. What focal-length eyepiece should be used to achieve a total magnification of 200X? The microscope has a tube length L=160mm

### Motion Along an Inclined Plane: Example Problems

1. A 300 kg. piano slides 4.5m down a 25 degree incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. Calculate: A) The force exerted by the man, B) The work done by the man on the piano, C) The work done by the friction force,