Answer and Explanation:
Commutator are used in DC machine commutator is mainly used for the reversing the direction of the current .It is connected to the armature of the DC generator or motor
ADVANTAGE OF COMMUTATOR The main advantage of the commutator in DC motor is to keep keep the direction of the toque always in the same direction by changing the current direction
DISADVANTAGE OF COMMUTATOR : The main disadvantage is due to the friction between the commutator and brushes there is a friction loss.
Answer:
Assumption:
1. The kinetic and potential energy changes are negligible
2. The cylinder is well insulated and thus heat transfer is negligible.
3. The thermal energy stored in the cylinder itself is negligible.
4. The process is stated to be reversible
Analysis:
a. This is reversible adiabatic(i.e isentropic) process and thus 
From the refrigerant table A11-A13

sat vapor
m=

b.) We take the content of the cylinder as the sysytem.
This is a closed system since no mass leaves or enters.
Hence, the energy balance for adiabatic closed system can be expressed as:
ΔE
ΔU
)
workdone during the isentropic process
=5.8491(246.82-219.9)
=5.8491(26.91)
=157.3993
=157.4kJ
Answer:
Vertical; horizontal.
Explanation:
The Virginia Department of Motor Vehicles started issuing sets of newly designed driver's licenses to drivers in 2009. Although, the cards that were issued to drivers prior to the introduction of the new cards remained valid until they were expired.
There are two categories (shapes) for the Virginia driver's license. The vertical shape license represents the driver who is under the age of 21, and the horizontal shaped license represents the driver who is over the age of 21.
Additionally, the Virginia's driver license (vertical in shape) issued to drivers who are under the age of 21 has a background image of a dogwood flower while the horizontal shaped license issued to drivers who are over the age of 21 has a background image of the state capitol.
Answer:
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