Download Chapter 15 1. What current is needed to generate a 1.0 x 10

Chapter 15
1. What current is needed to generate a 1.0 x 10-7T magnetic field 1.0m
away from a straight wire?
2. A hall probe sits in a magnetic field of strength 0.2 T. If the probe has a
sensitivity of 100mV/T, what voltage (in mV) does the probe put out?
3. What is the strength of a magnetic field inside a solenoid of length 0.03m
long with 2000 turns and a current of 0.1A flowing through it?
4. The police have a new weapon in their arsenal against crime, a type of
magnetic cannon. The magnetic cannon consists of a solenoid mounted on
the front of the police car. During a car chase a large current is dumped into
the solenoid generating a large magnetic pulse, which passes into the car
being chased and “zaps” the car’s computer disabling the vehicle. Suppose
500A is dumped into the cannon, which has 500 turns and is 0.1m long.
What is the magnetic field generated?
5. The Earth has a magnetic field strength of 5.2 x 10-5T. How many times
stronger is the strength of the magnetic field in the previous problem
compared to the Earth’s field?
6. What is the magnetic field 0.2m away from the power cord of a 1100W,
110V hair dryer?
7. A hall probe measures the strength of a magnetic field. If the probe has a
sensitivity of 10.0 V/T, and a field strength of 0.02T is being measured, what
is the voltage measured on the probe?
8. An electromagnet is used in a buzzer. The buzzer consists of a coil of
length 0.01m, and 80 turns of wire. The coil has an iron core that increases
its permeability by a factor of 1000. What is the strength of the magnetic
field if 0.1A is flowing through the coil?
9. The automatic flusher on urinals consists of a sensor to detect your
presence and a spool valve, which is a type of solenoid valve that controls
the flow of water. The solenoid is a coil with a rod that moves in and out of
it. When current is applied to the solenoid the rod retracts into the solenoid
allowing the water to flow. If the coil is 0.05m long with 1000 turns, and
0.1A flows through it, what is the magnetic field in the center of the coil?
10. Another unit for magnetic field is the Gauss. 1 Tesla = 10,000 Gauss.
The Earth’s magnetic field is 5.2 x 10-5T. What is this field in Gauss?
11. If the current in a straight wire increases two times, how many times
does the magnetic field surrounding it increase?
12. If the distance a magnetic field being measured from a wire carrying
current increases two times, how many times does the field decrease?
13. A motor turns electrical energy into rotational energy. If a motor has an
efficiency of 90% and consumes 5000J on energy, what rotational energy is
generated?
14. A generator turns rotational energy into electrical energy. If the
generator has an efficiency of 90% and creates 40,000J of electrical energy,
what was the input of rotational energy?
15. An electromagnet creates a lifting force of 200 Lb when a current of
100A is running through it. How many amps are needed to lift 300Lb?
16. How close does one have to be near a wire carrying 15A in order to
measure a magnetic field of 0.25T?
17. An induction stove creates heat in a metal pot by generating a current in
it through electromagnetic induction. If the resistance across the pot is
2 x 10-3 ohms, and a current of 300A is flowing through the pot, how many
watts of heat is being created in the pot?
18. A solenoid is an electromagnetic coil with a core that can move in and
out. If the field inside a coil with a length of 0.01m and has 5A running
through it is 0.35T, how many turns does it have?
19. The electrical energy meter on every house measures the current,
voltage, and time the current is flowing, to determine how much energy is
being used, and therefore how much to charge you. If 50A is being drawn at
110V for 500s, how much energy was used?
20. What is the resistance of the coil in a superconducting magnet at its
operating temperature?