1. A transformer has a primary coil and a secondary coil with the number of loops are 500 and 5000. Input voltage is 220 V. What is the output voltage?
Known :
Primary coil (NP) = 500 loops
Secondary coil (Ns) = 5000 loops
Primary voltage (VP) = 220 Volt
Wanted : Secondary voltage (VS)
Solution :
Vs / Ns = Vp / Np
Vs / 5000 = 220 / 500
Vs / 5000 = 0.44
Vs = (0.44)(5000)
Vs = 2200 Volt
[irp]
2. A transformer has primary coil with 1200 loops and secondary coil with 1000 loops. If the current in the primary coil is 4 Ampere, then what is the the current in the secondary coil.
Known :
Primary coil (NP) = 1200 loops
Secondary coil (NS) = 1000 loops
The current in the primary coil (IP) = 4 Ampere
Wanted: The current in secondary coil (IS)
Solution :
IS/IP = NP/NS
The current in the secondary coil :
IS/4 = 1200/1000
IS/4 = 1.2
IS = 1.2 (4)
IS = 4.8 Ampere
3. The secondary voltage is 220 Volt and primary voltage is 110 volt, then a comparison of the secondary coil and primary coil is…
Known :
Secondary voltage (VS) = 220 Volt
Primary voltage (VP) = 110 Volt
Wanted : NS/NP
Solution :
VS/VP = NS/NP
220/110 = NS/NP
22/11 = NS/NP
2/1 = NS/NP
12/6 = NS/NP
[irp]
4. Based on figure below, what is the primary voltage of the transformer.
Known :
Secondary voltage (VS) = 24 Volt
Primary loops (NP or N1) = 11 N
Secondary loops (NS or N2) = 1 N = N
Wanted : Primary voltage (VP)
Solution :
Vs / Ns = Vp / Np
24 / N = Vp / 11 N
24 / 1 = Vp / 11
24 = Vp / 11
Vp = (24)(11)
Vp = 264 Volt
5. Based on figure below, what is the input voltage of the transformer.
Known :
Primary coil (N1) = 21 N
Secondary coil (N2) = 3 N
Secondary voltage (V2) = 20 Volt
Wanted : Primary voltage (V1)
Solution :
V2 / N2 = V1 / N1
20 / 3 N = V1 / 21 N
20 / 1 = V1 / 7
20 = V1 / 7
V1 = (7)(20)
V1 = 140 Volt
[irp]
6. According to figure below, what is the amount of the secondary loops of the transformer.
Known :
Primary voltage (VP) = 220 Volt
Primary loops (NP) = 200 loops
Secondary voltage (VS) = 1100 Volt
Wanted : Secondary loops (NS)
Solution :
Vs / Ns = Vp / Np
1100 Volt / Ns = 220 Volt / 200 loops
1100 / Ns = 220 / 200
1100 / Ns = 1.1
Ns = 1100 / 1.1
Ns = 1000 loops
[irp]
7. According to figure below, what is the amount of the secondary loops of the transformer.
Known :
Primary voltage (VP) = 220 Volt
Primary loops (NP) = 200 loops
Secondary voltage (VS) = 1100 Volt
Wanted : Secondary loops (NS)
Solution :
Vs / Ns = Vp / Np
1100 / NS = 220 / 200
1100 / NS = 22 / 20
1100 / NS = 1.1
NS = 1100 / 1.1
NS = 1000
8.
| Transformer | Np | Ns | Vp | Vs | Ip | Is |
| 1 | 1000 | 120 | 12 | 0.4 | 2 | |
| 2 | 80 | 8 | 20 | 2 | 2.5 |
Based on the above table, if the efficiency of both transformers is the same, 50%, Determine Ns and Ip.
Solution :
The equation of transformer’s efficiency :
Calculate Ns of the transformer 1 :
Calculate Ip of the transformer 2 :
9.
Based on the above figure, which of the following statements about the figure above is correct.
A. Figure 1 is a step-up transformer and figure 2 is a step-down transformer
B. Figure 1 is a step-down transformer and figure 2 is a step-up transformer
C. Figure 1 and 2 are a step-down transformer
D. Figure 1 and 2 are a step-up transformer
Solution
Step-up transformer serves to raise the electrical voltage while the step-down transformer to reduce electrical voltage. In Figure 1, the primary voltage is greater than the second voltage (20 Volts > 5 Volts) so that Figure 1 is a step-down transformer. In Figure 2, the primary voltage is smaller than the second voltage (5 Volts < 40 Volts) so that Figure 2 is a step-up transformer.
The correct answer is B.
10.
If the primary coil has 800 loops, then determine the secondary coil.
Known :
Primary loops = Np = 800 loops
Primary voltage =VP = 220 Volt
Secondary voltage = VS = 55 Volt
Wanted : Secondary loops (NS)
Solution :
Vs / Ns = Vp / Np
55 / Ns = 220 / 800
55 / Ns = 22 / 80
NS = (80)(55) / 22
NS = 4400 / 22
NS = 200 loops
11.
The correct statement about transformer P and Q is…
A. P is a step-down transformer because of Is < Ip
B. P is a step-up transformer because of Vp < Vs
C. Q is a step-up transformer because of Vp > Vs
D. Q is a step-up transformer because Is > Ip
Solution
P is step-up transformer because primary voltage (Vp = 110 V) < secondary voltage (Vs = 200 V).
Q is step-down transformer because primary voltage (Vp = 220 V) > secondary voltage (Vs = 110 V).
The correct answer is B.
