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4 years ago

I) A 100 W and 60 W bulb are joined in series and connected to the mains. Which bulb

Physics

1 answer:

kolbaska11 [484]4 years ago

3 0

Answer:

i) 60 W

ii) 100 W

Explanation:

In each case, the bulb that dissipates the most power is the bulb that glows brighter. Power is voltage times current (P = VI). Using Ohm's law, we can rewrite this as P = I²R or P = V²/R.

Bulbs are rated at a certain power for a certain voltage. P = V²/R, so the bulb with the lower resistance will have the higher power rating. Therefore, the 100 W bulb has a lower resistance than the 60 W bulb.

i) They are in series, so they have the same current. P = I²R, so the bulb with the higher resistance will glow brighter. That's the 60 W bulb.

ii) They are in parallel, so they have the same voltage. P = V²/R, so the bulb with the lower resistance will glow brighter. That's the 100 W bulb.

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A 3.50 cm tall object is held 24.8 cm from a lens of focal length 16.0 cm. What is the image height?

Mandarinka [93]

Answer:

Explanation:

Using the formula to first get the image distance

1/f = 1/u+1/v

f = focal length of the lens

u = object distance

v = image distance

Given f = 16.0 cm, u = 24.8 cm

1/v = 1/16 - 1/24.8

1/v = 0.0625-0.04032

1/v = 0.02218

v = 1/0.02218

v = 45.09 cm

To get the image height, we will us the magnification formula.

Mag = v/u = Hi/H

Hi = image height = ?

H = object height = 3.50 cm

45.09/24.8 = Hi/3.50

Hi = (45.09*3.50)/24.8

Hi = 6.36 cm

The image height is 6.36 cm

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3 years ago

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3 years ago

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Two wires A and B with circular cross-section are made of the same metal and have equal lengths, but the resistance of wire A is

Nesterboy [21]

Answer:

r₁/r₂ = 1/2 = 0.5

Explanation:

The resistance of a wire is given by the following formula:

R = ρL/A

where,

R = Resistance of wire

ρ = resistivity of the material of wire

L = Length of wire

A = Cross-sectional area of wire = πr²

r = radius of wire

Therefore,

R = ρL/πr²

FOR WIRE A:

R₁ = ρ₁L₁/πr₁² -------- equation 1

FOR WIRE B:

R₂ = ρ₂L₂/πr₂² -------- equation 2

It is given that resistance of wire A is four times greater than the resistance of wire B.

R₁ = 4 R₂

using values from equation 1 and equation 2:

ρ₁L₁/πr₁² = 4ρ₂L₂/πr₂²

since, the material and length of both wires are same.

ρ₁ = ρ₂ = ρ

L₁ = L₂ = L

Therefore,

ρL/πr₁² = 4ρL/πr₂²

1/r₁² = 4/r₂²

r₁²/r₂² = 1/4

taking square root on both sides:

r₁/r₂ = 1/2 = 0.5

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4 years ago

FREE BRAINIEST IF YOU ANSWER THIS

Inessa [10]

The watt is a rate, similar to something like speed (miles per hour) and other time-interval related measurements.

Specifically, watt means Joules per Second. We are given that the electrical engine has 400 watts, meaning it can make 400 joules per second. If we need 300 kJ, or 3000 Joules, then we can write an equation to solve the time it would take to reach this amount of joules:

w * t = E

w: Watts

t: Time

E: Energy required

(Watts times time is equal to the energy required)

Input our values:

400 * t = 3000

(We need to write 3000 joules instead of 300 kilojoules, since Watts is in joules per second. It's important to make sure your units are consistent in your equations)

Divide both sides by 400 to isolate t:

$\frac{400t}{400}$ = $\frac{3000}{400}$