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3 years ago

In alternating current, how often does the current alternate between negatively and postively?

2 answers:

4 0

In an alternating current (AC) circuit the two poles alternate between negative and positive and the direction of the current (electron flow) reverses periodically.

strojnjashka [21]3 years ago

4 0

1/60th of a second each way back and forth

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Consider a Pitot static tube mounted on the nose of an experimental airplane. A Pitot tube measures the total pressure at the ti

kotykmax [81]

Answer:

M∞ = 0.53

M∞ = 1.5

M∞ = 3.1

Explanation:

Find: For each case the free stream Mach number.

-Pitot pressure=1.22×10^5N/m2 , static pressure=1.01 × 10^5N/m2 .

Solution:

- The free stream Mach number is a function of static to hydrodynamic pressures. So for this case we have:

P = 1.01 × 10^5 .. static pressure

Po = 1.22×10^5 ... pitot pressure ( hydrodynamic )

- Take the ratio:

P / Po = (1.01 × 10^5) / (1.22×10^5) = 0.8264.

- Use Table A.13 and look up the ratio P/Po = 0.8264 for Mach number M∞.

M∞ = 0.53

Find:

-Pitot pressure=7222 lb/ft^2 , static pressure=2116 lb/ft^2

Solution:

- The free stream Mach number is a function of static to hydrodynamic pressures. So for this case we have:

P = 2116 .. static pressure

Po = 7222 ... pitot pressure ( hydrodynamic )

- Take the ratio:

P / Po = (2116) / (7222) = 0.2930.

- However, since this is supersonic, a normal shock sits in front of the Pitot tube. Hence, Po is now the total pressure behind a normal shock wave. Thus, we have to use Table A.14.

P1 = 2116 .. static pressure

Po2 = 7222 ... pitot pressure ( hydrodynamic )

- Take the ratio:

Po2 / P1 = (7222) / (2116) = 3.412.

- Use Table A.14 and look up the ratio Po2/P1 = 3.412 for Mach number M∞.

M∞ = 1.5

Find:

-Pitot pressure=13197 lb/f^t2 , static pressure=1020 lb/ft^2

Solution:

- The free stream Mach number is a function of static to hydrodynamic pressures. So for this case we have:

P = 1020 .. static pressure

Po = 13197 ... pitot pressure ( hydrodynamic )

- Take the ratio:

P / Po = (1020) / (13197) = 0.0772.

- Again, since this is supersonic, a normal shock sits in front of the Pitot tube. Hence, Po is now the total pressure behind a normal shock wave. Thus, we have to use Table A.14.

P1 = 1020 .. static pressure

Po2 = 13197 ... pitot pressure ( hydrodynamic )

- Take the ratio:

Po2 / P1 = (13197) / (1020) = 12.85.

- Use Table A.14 and look up the ratio Po2/P1 = 12.85 for Mach number M∞.

M∞ = 3.1

3 0

3 years ago

The uniform beam is supported by two rods AB and CD that have crosssectional areas of 10 mm2 and 15 mm2 , respectively. Determin

ddd [48]

Answer:

w=2.25

Explanation:

It is necessary to determine the maximum w so that the normal stress in the AB and CD rods does not exceed the permitted normal stress.

The surface of the cross-section of the stapes was determined:

A_ab= 10 mm^2

A-cd= 15 mm^2

The maximum load is determined from the condition that the normal stresses is not higher than the permitted normal stress σ_allow.

σ_ab = F_ab/A_ab $\leq$ σ_allow

σ_cd = F_cd/A_cd $\leq$ σ_allow

In the next step we will determine the static size: Picture b).

We apply the conditions of equilibrium:

∑F_x=0

∑F_y=0

∑M=0

∑M_a=0 ==> -w*6*0.5*6*0.75*F_cd*6 =0

==> F_cd = 2*w*k*N

∑F_y=0 ==> F_cd+F_ab - 6*w*0.5 ==>2*w+F_ab -6*w*0.5 =0

==> F_ab = w*k*N

Now we determine the load w

Sector AB:

σ_ab = F_ab/A_ab $\leq$ σ_allow=300 KPa

= w/10*10^-6 $\leq$ σ_allow=300 KPa

w_ab = 3*10^-3 kN/m

Sector CD:

σ_cd = F_cd/A_cd $\leq$ σ_allow=300 KPa

= 2*w/15*10^-6 $\leq$ σ_allow=300 KPa

w_cd = 2.25*10^-3 kN/m

w=min{w_ab;w_cd} ==> w=min{3*10^-3;2.25*10^-3}

==> w=2.25 * 10^-3 kN/m

The solution is:

w=2.25 N/m

note:

find the attached graph

6 0

3 years ago

True or False - Blueprints can be drawn both by hand and on a computer

Orlov [11]

Answer:

The answer is true.

Explanation:

Most of it is done in computer, but it can also be drawn out by hand.

6 0

3 years ago

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Giving free brainlist first 1

kaheart [24]

Hi! Hope you're having a great day!

8 0

3 years ago

Calculate the gear ratio below if the blue gear is the driver

alexandr402 [8]

Answer:

The correct option is;

Explanation:

The number of teeth on the blue, driver, gear = 20 T

The number of teeth on the yellow, driven, gear = 20 T

In order to find the gear ratio of a gear train, the ratio of the number of teeth on the driven gear to the number of teeth on the driver gear gives the gear ratio

Therefore, the gear ratio = 20 T/(20 T) = 1

7 0

3 years ago