Physics 1142 Test
State Faraday's laws of electrolysis:
1. The mass of an element released at an electrode during electrolysis by a steady current is directly proportional to the quantity of electric current passing through the electrolyte. 2. The mass of a substance liberated at the electrodes during electrolysis by a steady current is proportional to the equivalent mass of that substance.
Number the following events in chronological order: The copper plate (anode) conducts electrons into the electrolyte solution. The sulfuric acid solution dissociates into sulfate ions and hydrogen ions. The zinc cathode dissolves, releasing positive zinc ions and giving the zinc electrode a negative charge. The zinc cathode dissolves completely, stopping the reaction. The electrons are received by positive hydrogen ions, forming hydrogen gas.
3 1 2 5 4
You are given six cells, each capable of delivering .25 amp at 1.5 volts. Tell how many cells are needed, and how they are connected, in each situation. a circuit needing .75 amp current at 1.5 volts a circuit needing .25 amp current at 7.5 volts a circuit needing 1.50 amp current at 1.5 volts
3 cells in parallel 5 cells in series 6 cells in parallel
State Lenz's Law
A current induced by electromagnetic forces always acts to oppose those forces.
Joseph Henry
Discovered electromagnetic induction at the same time as Michael Faraday
Heinrich Lenz
Discovered induced currents that oppose electromagnetic forces
Humphry Davy
Discovered that electrolysis could free metals from their ores
Lee De Forest
Established a radio station
John Fleming
Invented the diode
William Shockley
Invented the transistor
cathode
Negative electrode
On a residential street, 115 volt current is supplied to the houses from a transformer whose primary voltage is 2300 volts. How many turns are needed on the secondary coil for every 100 turns on the primary transformer coil?
Refer to M(72) in Pace for solution
How much mercury is liberated by passing a current of 10.0 amps for a period of 14.0 hours? Mercury has an equivalent mass of 100.30.
Refer to N(77) in Pace for solution
How long will it take for a current of 5.00 amps to release 15.0 grams of aluminum, which has an equivalent mass of 9.00?
Refer to N(79) in Pace for solution
If the average current and voltage in an alternating current electrical circuit are 12.0 volts and 5.50 amps, what are the maximum current and voltage in the circuit?
Refer to U(62) in Pace for solution
Describe the voltage and resistance characteristics of battery cells connected in parallel.
The total voltage of the battery cells is the same as for a single cell. The total internal resistance of the cells is less than that of any single cell in the circuit.
Explain how a semiconductor triode amplifies a weak alternating signal.
The weak current is sent to a triode base where it controls a much stronger current flow between emitter and collector.
Give two reasons why early electrical researchers preferred direct current.
They were more familiar with it. It is easier to analyze.
electrochemical cell
battery cell that uses chemical reactions to produce electrical current flow
direct current
current that flows in only one direction
alternating current
current that reverses its direction of flow periodically
oxidation
loss of electrons
dry cell battery
main advantage is spill proof electrolyte
George Westinghouse
preferred alternating current for commercial use
anode
Positive electrode
Thomas Edison
preferred direct current for his experiments
electric motor
uses electricity to produce mechanical motion
electric generator
uses mechanical motion to produce electricity
Alessandro Volta
discovered the voltaic cell, made the first battery
fuel cell
extremely efficient
Michael Faraday
first discovered two laws of electrolysis
reduction
gain of electrons
What is self-induction?
the destructive interaction between a current and the magnetic field it produces.
