Physics 1141 Test

What is a field?

a region in space in which a body's magnetic, electric, or gravitational fore exerts its influence.

The sum of the resistances in a parallel circuit always exceeds the total resistance of the circuit.

true

Total resistance in a parallel circuit is always less than any individual resistance in the circuit.

true

parallel electric circuit

voltage is the same in each resistance

State Ohm's law.

Current is directly proportional to electric potential and inversely proportional to resistance.

List 3 ways a magnetic substance can lose its magnetism

1. heat 2. interaction with another magnetic field 3. mechanical action

List the 4 factors that determine the resistance of an electrical wire.

1. type of material 2. length of the wire 3. diameter of the wire 4. temperature

Andre Ampere

first experimented with solenoids

What is a paramagnetic metal?

one that is weakly attracted by a magnet

Higher voltage generates greater power provided the current remains the same.

true

James Clerk Maxwell

described magnetism, light, and electricity with a set of four mathematical equations.

When a magnetic north pole with a strength of 70 units is placed 3 cm from another magnetic pole in air, it experiences an attractive force of 1200 dynes. What is the strength of the second pole?

Refer to F(57) in Pace for solution

An electric heater operating on a 12 volt circuit has a resistance of 8.5 ohms. What current does it draw?

Refer to Q(31) in Pace for solution

What current will flow in a 240 volt circuit if the total resistance of the circuit is 80 ohms?

Refer to Q(31) in Pace for solution

A 12 volt automobile battery furnishes 1.75 amps to an incandescent light. What is the resistance of the light?

Refer to R(32) in Pace for solution

A 12 volt automobile battery is rated to supply 550 amps for cold starting. What is the resistance of the starter motor during such a cold start?

Refer to R(32) in Pace for solution

An electric toaster with a resistance of 12. 5 ohms draws a current of 9.6 amps. What is the voltage of the circuit?

Refer to R(35) in Pace for solution

magnetic flux density

number of magnetic flux lines per unit area

What is a diamagnetic metal?

one that is slightly repelled by a magnet

What is a ferromagnetic metal?

one that is strongly attracted by a magnet

What are magnetic domains?

groups of millions of magnetic atoms aligned the same way

State the 3 laws of magnetism

1. Either pole of a magnet attracts a nonmagnetic ferromagnetic metal 2. Like magnetic poles repel one another 3. Unlike magnetic poles attract one another

magnetic declination

the difference between geographic north and magnetic north

series electric circuit

current is the same in each resistance

geographic poles

North Pole and South Pole of Earth

A 100 watt light bulb has lower resistance than a 40 watt light bulb.

true

A larger current will increase the power generated in a circuit if the voltage remains unchanged.

true

Resistances of 3 ohms and 5 ohms are connected in series with a battery. An ammeter in the circuit reads .75 amp. What is the voltage in the circuit? What is the current if the resistances are connected in parallel and the voltage remains the same?

Refer to V(84) in Pace for solution

State the left-hand rule for magnetic fields around current-carrying wires.

When a wire is grasped with the left hand so that the thumb points in the direction of electron flow, the fingers will be pointing in the direction that the magnetic lines of force are flowing.

electron flow

always a source of negative electric potential to a positive electric potential

magnetic poles

always appear in north and south pairs

magnetic dip

angle of inclination of dip compass

Joseph Henry

designed electromagnets that made the telegraph

Michael Faraday

developed field theory to explain magnetism

Both current and voltage are the same through each branch of a parallel circuit.

false

Electrons flow through a circuit from the positive terminal to the negative terminal.

false

The heating effect in an electrical circuit is inversely proportional to the current in the circuit.

false

Hans Christian Oersted

first demonstrated the induction of magnetism by electric flow

Georg Simon Ohm

first studied current, electric potential, and resistance

The sum of the resistances in a series circuit always exceeds the total resistance of the circuit.

false